The Combined Effect of Cold Work and Chloride Content on Corrosion Mechanism of 2101 Lean Duplex Stainless Steel in Citric Acid

The Combined Effect of Cold Work and Chloride Content on Corrosion Mechanism of 2101 Lean Duplex Stainless Steel in Citric Acid | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The Combined Effect of Cold Work and Chloride Content on Corrosion Mechanism of 2101 Lean Duplex Stainless Steel in Citric Acid Mohammadreza Mokhtare, Mazdak Izadi, Saeid Karimi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6483885/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract 2101 Lean duplex stainless steel (LDX) is emerging as a strong competitor to traditional austenitic stainless steels in the food industry, thanks to its superior corrosion resistance and cost-effectiveness. This study investigates the impact of 15, 30 and 45% cold working and chlorine content on the corrosion behavior of LDX 2101 exposed to citric acid as the most common electrolyte in food industries. Detailed electrochemical and characterization techniques have been used in this study. The results reveal that 2101 LDX is composed of γ and α phases, with Cr 2 N and M 23 C 6 precipitates forming along grain and phase boundaries. Cold working primarily deforms the γ phase, leading to the formation of strain-induced martensite (SIM), and increases the hardness of α and γ phases. Galvanic and pitting corrosion was observed, especially in the α phase, where Cr 2 N precipitates act as pit initiation sites. While the presence of chloride ions accelerated corrosion rate, cold working enhanced the materials corrosion resistance by promoting the surface passive layer characteristics. Electrochemical impedance spectroscopy results indicated that the as-annealed sample showed the lowest corrosion resistance after 24 h of immersion. In contrast, samples subjected to 15% and 30% strain exhibited improved resistance with 23.5 and 46.7% reduction in i corr , with a significant passive behavior observed in the 45% cold-worked sample. Physical sciences/Chemistry Physical sciences/Engineering Physical sciences/Materials science LDX 2101 EIS pitting corrosion cold work strain-induced martensite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 1 Introduction Duplex stainless steels (DSS) are a family of steels known as two-phase due to their structure, which consists of austenite (γ) with a face-centered cubic (FCC) crystal structure and ferrite (α) with a body-centered cubic (BCC) crystal structure 1 . Traditional stainless steels, such as 304 and 316L have been replaced by DSS due to their superior mechanical properties and excellent corrosion resistance 2 – 4 . Lean duplex stainless steels (LDX) are a subset of the duplex stainless-steel family. By reducing expensive elements like Ni and Mo and adding γ-stabilizer elements such as Mn and N to the chemical composition, LDX are not only more economical but also have fewer harmful phases, such as σ and χ, due to their lower alloying elements 5 , 6 . Furthermore, the addition of N in LDX improves both the corrosion resistance and strength/formability. The most important representatives of LDX include 2101 LDX, SAF 2304, and AL 2003 7 . LDX 2101 is an economical two-phase stainless steel with lower Ni and Mo content, offering corrosion properties similar to those of commercial single-phase or two-phase stainless steels 8 . This steel is designed to form less martensite in γ and exhibits uniform corrosion properties superior to those of grade 304 stainless steel, with localized corrosion resistance comparable to that of 316L. It also offers better chloride stress corrosion cracking resistance than austenitic steels, including 304, making it a suitable substitute for these stainless steels 9 . Based on transmission electron microscope (TEM) investigations, in addition to the α and γ phases, Cr₂N and Cr₂₃C₆ phases are also formed in LDX 2101 10 . Due to the absence of Mo and the high percentage of N, the formation of nitride phases in LDX 2101 creates areas that are sensitive to pitting corrosion 11 . Additionally, in LDX 2101, the α-phase exhibits lower corrosion resistance, making it more susceptible to both galvanic and pitting corrosion. 12 . Nevertheless, the formation of a passive layer protects the surface of LDX 2101 against corrosion, even in harsh chloride environments 13 . Additionally, due to the presence of N, the γ phase forms a better protective layer, making LDX 2101 resistant to pitting corrosion in chloride environments at temperatures below 10°C 14 . One of the most important post-process fabrication methods for producing metal parts and tools is cold plastic deformation, which influences the final properties of steels 15 . LDX 2101 is a transformation-induced plasticity (TRIP) steel that offers varying mechanical properties depending on the γ/α phase fraction 16 . According to Fuertes et al. 17 , cold plastic deformation in LDX 2101 induces the formation of martensite and mechanical twins in the γ phase. In another study by Zhang et al. 18 , it was reported that cold work primarily causes dislocation slip in the α phase, leading to the formation of dislocation cells and deformation microbands. On the other hand, in the γ phase, strain-induced martensite (SIM) and twinning are observed 18 . LDX 2101 is used in the food industry due to its superior corrosion resistance and cost-effectiveness and exhibits better corrosion behavior compared to 430 and 316L steels in the environments of the whey and dairy industries 19 . Among the organic acids found in the food industry, citric acid is particularly corrosive and is present in foods such as tomatoes and lemons 20 – 22 . According to Mazinanian et al. 23 , the rate of metal release due to corrosion in LDX 2101 in tap water and citric acid environments at temperatures of 40°C and 70°C meets the Council of Europe standards. This makes LDX 2101 a leading candidate for use in the food industry. Based on the literature review and the applications of LDX 2101 in the food industry, this study aims to address this gap by systematically investigating the influence of cold work and varying concentrations of chloride/citric acid on the corrosion behavior of LDX 2101. For this purpose, detailed electrochemical investigations and immersion tests were conducted. Surface evolutions after corrosion were examined using optical microscopy (OM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Cold compression testing, work hardening rate assessment, macro and microhardness testing, and X-ray diffraction (XRD) analysis were performed. This research provides a better understanding of the working process and conditions for using LDX 2101 in the food industry and its post-fabrication processes. 2 Materials and method The rolled and annealed ingot of LDX 2101 stainless steel with a thickness of 9 mm and chemical composition detailed in Table 1 was prepared. The phase diagram of the alloy was calculated using JMatPro software based on the chemical composition from Table 1 . To achieve a 50–50 phase fraction of α and γ, the rolled and annealed ingot was heat-treated at 670°C for 2 h and then cooled in air. Nine samples, each with dimensions of 9×10×10 mm 3 , and six cylindrical samples with a diameter of 5 mm and a height of 9 mm were prepared using a wire-cutting method. The surface of the samples was chosen to be perpendicular to the rolling direction to investigate the properties. To apply plastic deformation to the cylindrical samples, cold compression tests were conducted using a Santam STM50 machine at a strain rate of 0.01 s − 1 . Strains of 15%, 30%, and 45% were applied to the samples, which were then cut diagonally in half from the middle using a wire cutter for further investigation. The surfaces of the samples were prepared using sandpaper ranging from 80 to 3000 mesh, followed by polishing with a nano-alumina solution. For metallography, the samples were electrolytically etched using a solution of 50 g/L KCl in distilled water, with the samples acting as the anode under a voltage of 5 V for 10 s. The Vickers hardness of the samples was measured using a universal testing device with a force of 980 N and a dwell time of 15 s. Additionally, the Vickers microhardness of each phase was examined using a Koopa MH4 machine with a force of 1 N and a 15-second dwell time. In the hardness tests, five measurements were taken for each sample/phase, and the average results were reported. Table 1 Chemical Composition (wt%) of LDX 2101 Investigated in This Research Element Cr Cu Mn Mo Ni Si C N Fe Percentage 21.57 0.3 5.13 0.28 1.56 0.65 0.025 0.23 Base. To investigate the corrosion properties of the samples, solutions of 5 and 50 g/L citric acid with 0, 0.01, and 0.2 M NaCl were prepared. A concentration of 5 g/L of citric acid is considered standard in the food industry 19 . Cyclic Voltammetry (CV), Potentiodynamic Polarization (PDP), and Electrochemical Impedance Spectroscopy (EIS) tests were conducted using radstat200 machine to assess the corrosion properties of the samples in different solutions and at different strain levels. All electrochemical tests were conducted in a common three-electrode cell (counter electrode: Platinum, Reference electrode: Ag/AgCl). Before performing the corrosion tests, in the CV analysis, the samples were immersed in solutions with varying citric acid and NaCl concentrations for 2 h to reach a stable open circuit potential (OCP). For the PDP test on the strained samples, this time was extended to 24 h to ensure a stable OCP. The EIS measurements were done in the frequency range of 100000 Hz to 0.1 Hz at OCP. The sinusoidal stimulus potential was 0.01 V. Additionally, an immersion test was performed on undeformed samples in three solutions: 5 g/L citric acid, and 5 g/L citric acid with 0.01 and 0.2 M NaCl for one week. For the 15%, 30%, and 45% cold-worked samples, the immersion test was conducted in a solution of 0.2 M NaCl and 5 g/L citric acid for 168 h. Mass changes during the immersion test were measured using an A&D GR-200 scale with an accuracy of 0.0001 grams. To examine the phase evolutions of the samples after cold work, X-ray diffraction (XRD) tests were performed using a Panalytical PW3050 device equipped with a Cu cathode. Optical microscope (OM) images were captured using a Dewinter DG-VICTORY microscope. For surface examination, an FEI Quanta 200 scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) probe was used. Additionally, a BRISK atomic force microscope (AFM) was employed to assess the surface morphology and roughness of the α phase after being corroded in the immersion test. 3 Results and discussion 3.1 Microstructural evolutions after cold work Figure 1 shows the equilibrium phase diagram of LDX 2101 simulated using JMatPro software. As illustrated, this stainless steel consists of two main phases, α, and γ, whose fractions vary according to the heat treatment temperature. However, at temperatures of 670°C and 1130°C, the fraction of these two phases is equal. In addition to the α and γ phases, the formation of M 23 C 6 carbides and M 2 N nitrides, both rich in chromium, is predicted in this alloy. The prediction results from Thermo-Calc software similarly indicate the presence of α, γ, chromium-rich carbides, and nitride phases with the same phase fraction, consistent with the JMatPro predictions 24 . Although there is a possibility of spinodal decomposition in DSSs with 21% chromium and above, a temperature of 670°C was chosen to achieve a structure with an equal phase fraction of α and γ, because spinodal transformation does not occur in LDX 2101 at temperatures above 600°C 25 . Figure 2 a shows the true stress-strain diagram for the cold compression test. Based on the linear region of elastic deformation, the compressive yield stress of 578 MPa was obtained for LDX 2101. Figure 2 b illustrates that the rate of work hardening is extremely rapid up to a strain of approximately 11%. Beyond this strain, work hardening occurs at a relatively constant rate due to cold deformation. The hardness test results in Fig. 2 c indicate a significant increase in hardness due to cold work, with a 152% increase after 45% strain. However, the rate of hardness increase does not match the rate of strain hardening, suggesting the influence of other factors on hardness. It is noteworthy that LDX 2101 has a two-phase structure (Fig. 2 b) consisting of α and γ. These two phases exhibit different strengths and hardness, and due to the difference in plasticity between the BCC and FCC crystal structures, work hardening occurs differently in these phases. To investigate the effects of cold work on each phase, Fig. 2 d presents the dislocation density diagram for the α and γ phases, calculated using the Williamson-Hall 26 relationship based on the XRD data shown in Fig. 3 . As observed, cold work consistently increases the dislocation density in the γ phase, whereas the dislocation density in the α phase increases at a lower rate and shows minimal change, even in the strain range of 15–30%. Similarly, it has been reported that during the cold deformation of LDX 2101, the γ phase experienced more deformation in cold rolling. Generally, the γ phase, with its FCC crystal structure, is softer and more plastically deformable than the BCC α phase at room temperature 27 . Based on the literature review, the formation of SIM in LDX 2101 due to the cold work has been reported. Unfortunately, it is not possible to detect martensite by the usual methods like SEM due to the non-diffusive nature of this transformation. Additionally, the crystal structure of martensite is BCC, with a lattice parameter very close to the α phase 28 . Based on the XRD graphs in Fig. 3 , as the strain level increases, the diffraction peak intensity of γ (200) decreases, and the α (200) increases. This observation may be associated with the transformation of γ to α′-martensite 29 . The peaks related to Cr 2 N were also observed with increasing strain. However, due to the small phase fraction of these phases (less than 2 wt. %, as predicted by JMatPro), they are not detectable by XRD. To better investigate strain-induced phase transformations, Fig. 4 shows the microhardness test results for the α and γ phases after cold working, taken from the central regions of cylindrical samples. As observed, in the annealed sample, the hardness of the α phase is higher than that of the γ phase. However, after cold working, the hardness of the γ phase increases significantly, while the α phase becomes slightly harder only after 45% strain. The increase in hardness of the γ phase can be attributed to two main factors: first, the increase in dislocation density, which increases the hardness of this phase; and second, the formation of SIM in γ, which significantly contributes to the hardness. According to Bassani et al. 27 , the utilization of EBSD analysis in LDX 2101 revealed that hardness increment due to the work hardening occurred up to a 20% strain caused by cold working. Once the strain exceeds 20%, the formation of α′-martensite becomes the main factor contributing to the strength increase. Moreover, Chen et al. 30 reported that α′-martensite formed after multiple shot peening of SAF 2507 DSS, with approximately 31.6% α′-martensite observed on the impacted surface of the triply peened specimen. However, according to Fig. 2 c, the hardness of the sample after 45% strain (380 HV) is higher than that of both the α and γ phases. This suggests the influence of additional factors on hardness increase, such as the Hall-Petch effect 31 and the formation of Cr 2 N phases, which are discussed in the following sections. 3.2 Effects of Cl/Citric Acid on Corrosion Properties Figure 5 shows the CV diagrams for the annealed sample of LDX 2101, exposed to 5 and 50 g/L citric acid with 0, 0.01, and 0.2 M NaCl at room temperature. The extracted data from the curves in Fig. 5 , including corrosion potential ( E corr ), corrosion current density ( i corr ), pitting corrosion protection potential ( E pp ), and the pit nucleation resistance ( E pn = E pp - E corr ) are reported in Table 2 . As seen in Fig. 5 a and Fig. 5 d, in non-chloride solutions, no hysteresis loop is observed, indicating that pitting corrosion does not occur in the citric acid solution. According to the data in Table 2 , increasing the concentration of citric acid results in a decrease in E corr and an increase in i corr , indicating lower resistance to uniform corrosion and faster kinetics at higher acid concentrations 32 . Additionally, images of the corroded sample surfaces in Fig. 5 a and Fig. 5 d show no pits, only preferential corrosion of the α phase. According to Fig. 5 , after the addition of 0.01 M NaCl, the corrosion mechanism changes, and pitting corrosion was observed in all samples. Generally, increasing the chloride concentration from 0.01 M to 0.2 M, significantly reduced the pitting corrosion resistance. As shown in Table 2 , the resistance to pit nucleation decreases with increasing chloride and citric acid concentrations. A noteworthy observation is the combined effect of high concentrations of chlorine and citric acid on pitting corrosion resistance. As both concentrations increase, the pitting resistance decreases significantly, as evident from the corroded surface after the CV test (Fig. 5 e). However, in the 50 g/L citric acid solution, the E corr in the 0.2 M NaCl solution is slightly higher compared to 0.01 M. The worst values of E pn were recorded for the 50 g/L citric acid + 0.2 M NaCl solution, highlighting a critical reduction in pitting corrosion resistance. The pit repassivation is observed for 5 g/L citric acid + 0.01 M NaCl, 5 g/L citric acid + 0.2 M NaCl, and 5 g/L citric acid + 0.2 M NaCl samples. However, the repassivation process is disrupted in the 50 g/L citric acid + 0.2 M NaCl solution due to the increase corrosivity of the electrolyte and the destructive effect of chloride ions. Table 2 Corrosion parameters extracted from the CV diagrams of Fig. 5 after 2 h of immersion at room temperature. solution i corr (A/cm 2 ) E corr (V) E pp (V) E pn (V) Citric Acid NaCl 5 g/L 0.00 M 5.05×10 − 6 -0.256 - - 0.01 M 2.61×10 − 6 -0.418 0.349 0.767 0.20 M 9.74×10 − 5 -0.463 0.113 0.576 50 g/L 0.00 M 1.28×10 − 5 -0.369 - - 0.01 M 4.40×10 − 5 -0.382 0.336 0.718 0.20 M 3.92×10 − 5 -0.374 -0.025 0.349 To gain a deeper understanding of the corrosion process in samples treated with varying concentrations of citric acid and NaCl, Fig. 6 displays the microstructure of the corroded surface of annealed LDX 2101. The results of EDS analysis of the areas marked in Fig. 6 are also reported in Table 3 . As seen in Fig. 6 a, in the etched sample of LDX 2101 after heat treatment, the two-phase microstructure is evident. According to the data in Table 3 , the α phase is richer in Cr, while the γ phase contains higher amounts of Mn and N. This is due to the gamma-genic nature of Mn and N, which, unlike Cr, have a greater tendency to dissolve in γ. The Pitting Resistance Equivalent Number (PREN) is a constant for each alloy or phase, calculated according to Eq. 1 for low-Ni and high-Mn/N steels based on their chemical composition 33 , 34 . The lower the PREN values, the lower the pitting corrosion resistance. According to the information in Table 1 , the PREN number for the α phase is lower than that for the γ phase (23.39 vs. 24.19), indicating that this phase is less resistant to pitting corrosion. PREN= %Cr + 3.3×%Mo + 16×%N (1) Table 3 EDS analysis (At. %) of the areas marked in Fig. 6 Condition Area phase C N O Cr Mo Mn Fe Ni As etched 1 Ferrite 0.01 0.02 - 22.87 0.06 5.07 70.69 1.28 2 Austenite 0.01 0.19 - 21.08 0.02 5.63 71.53 1.54 Citric acid 5 g/L + NaCl 0.00 M 3 Ferrite 0.01 0.01 2.6 23.24 0.07 5.15 67.74 1.18 4 Austenite 0.02 0.25 2.81 21.21 0.15 5.86 67.9 1.8 0.01 M 5 Ferrite 0.03 0.04 2.65 23.29 0.03 5.21 67.5 1.25 6 Austenite 0.03 0.21 2.77 21.3 0.16 5.51 68.36 1.66 7 Pit 0.04 0.45 2.83 21.33 0.06 5.39 68.19 1.71 0.20 M 8 Ferrite 0.02 0.01 2.06 23.1 0.05 5.25 68.23 1.28 9 Austenite 0.02 0.42 2.5 20.51 0.11 5.62 69.05 1.77 10 Pit 0.01 0.48 0.52 28.98 0.13 8.02 60.94 0.92 11 Cr 2 N 0.02 5.12 - 35.72 - 4.58 54.56 - According to Fig. 6 b, no pits were observed in the microstructure of the sample corroded in 5 g/L citric acid solution. However, the α regions and α grain boundaries were more severely damaged by corrosion. As shown in Figs. 6 c and 6 f, Cr 2 N precipitates formed at the grain boundary regions and the phase boundaries between α and γ. The EDS-11 data in Table 3 shows that these phases are rich in Cr and N. These areas create corrosion-sensitive sites due to Cr depletion from the matrix, leading to lower corrosion resistance of the grain boundary regions. Additionally, grain boundaries are high-energy regions, making them more susceptible to corrosion 35 . According to the EDS analysis of areas 3 and 4, the surface corroded in citric acid solution showed low amounts of O, and the Cr content in the α phase increased slightly, suggesting the formation of Cr 2 O 3 oxides on the surface. With the addition of 0.01 M NaCl to the citric acid solution (Figs. 6 d and 6 g), pits formed scattered throughout the α phases and at the interphase boundaries. Corrosion of the α boundaries was also observed. The chemical composition of area 7, which contains larger amounts of N, suggests pit formation in Cr 2 N areas. However, based on the EDS data from areas 5 and 6, the chemical composition of the surface after corrosion in citric acid with chloride does not differ significantly from that in citric acid alone. Increasing the NaCl concentration to 0.2 M led to more intense pit formation, as seen in Figs. 6 g and 6 h, with pits often occurring at α grain boundaries. The EDS analysis of areas 8 and 9 shows that the chemical composition of the corroded surface in both α and γ phases is similar, while the pits (marked as area 10) exhibit a significant increase in Cr and Mn. Additionally, the N content is highest in this area compared to others, indicating that nitrides are preferential sites for pitting corrosion. Other studies on the corrosion of 2101 LDX in chloride environments have reported similar findings. The α phase has a low solubility for N, and this element has a high diffusion coefficient in the BCC matrix of the α phase, resulting in the formation of Cr 2 N phases. These phases tend to form at the α grain boundaries or the α/γ interfaces, creating sensitive sites for pitting corrosion in chloride solutions 9 , 11 , 12 . However, in the presence of citric acid, the CV test results and SEM data indicate that the protective layer has been compromised due to the acidic environment. The absence of passive areas in the CV curves and the low percentage of O on the surfaces suggest that metal oxides are not stable under these conditions. Additionally, higher concentrations of the acid-chloride solution create more severe corrosion conditions. Therefore, it can be concluded that annealed 2101 LDX is effective only in environments with low concentrations of chlorine and citric acid across various industries. 3.3 Effects of cold strain on corrosion Figure 7 presents the mass change of all samples vs. time during the weight-loss test, recorded at room temperature. As shown in Fig. 7 a, minimal corrosion occurred over 168 h in the 5 g/L citric acid solution, whereas the addition of chloride significantly increased the rate of weight loss. The primary reason for the reduction in specific mass is the corrosion progress, dissolution, and instability of corrosion products on the metallic surface, which is most intense during the first 50 h, and then gradually slows over time. The immersion test results align with the CV test, further confirming the destructive effect of chloride, especially at high concentrations. To investigate the effects of cold work on the corrosion of annealed 2101 LDX, the immersion test was conducted under harsh conditions in a solution of 5 g/L citric acid and 0.2 M NaCl. The results of the specific mass changes are shown in Fig. 7 b. It is evident that strain increasing significantly reduces weight loss due to corrosion. For duplex stainless steel, overall corrosion resistance is influenced by the resistance of the weaker phase. Therefore, higher overall corrosion resistance can be achieved when the corrosion resistance of both phases is closely matched 36 . According to Guo et al. 16 , after investigating the corrosion of 2101 LDX in a chloride environment using Scanning Kelvin Probe Force Microscopy (SKPFM), galvanic corrosion occurs between the α and γ phases, with the α phase experiencing more corrosion due to its lower electron work function (EWF). EWF, defined as the minimum energy required to remove an electron from a surface, indicates that a region with a higher EWF, which has a cathodic potential, exhibits better corrosion resistance compared to a region with a lower EWF, which has an anodic potential. Under similar conditions, the phase with the lower EWF is more susceptible to preferential corrosion 37 . In addition to the lower resistance of the α phase in galvanic corrosion, as evidenced by SEM and OM data, this phase is also more susceptible to pitting corrosion due to its lower PREN. Considering all these factors, the AFM analysis results of the α phase after 168 h of immersion are presented in Fig. 8 to further investigate the corrosion behavior. According to Fig. 8 , the as-polished sample displays minimal surface roughness, while the α phase in the sample corroded in a 5 g/L citric acid + 0.2 M NaCl solution for 7 days exhibits the highest surface roughness, indicating a more damaged surface. Notably, the surface roughness of the α phase decreases with increasing strain, which is associated with the reduced corrosion of this phase, a finding that is also confirmed by the immersion data. To investigate the effect of cold plastic deformation on corrosion properties, PDP tests were conducted on samples subjected to cold strain and immersed for 24 h in a 5 g/L citric acid and 5 g/L citric acid + 0.2 M NaCl solution. The results are presented in Fig. 9 , and the extracted corrosion data ( E corr and i corr ) related to PDP graphs are reported in Table 4 . As shown in Fig. 9 a, the increase in cold strain generally led to a decrease in corrosion resistance in the 5 g/L citric acid solution. According to the data in Table 4 , in the chloride-free solution, the E corr steadily decreased with increasing cold work. Additionally, except for the 45% cold-worked sample, two other samples exhibited a negligible decrease in i corr . Thus, it can be concluded that corrosion resistance in the 5 g/L citric acid is not considerably affected by cold work. Furthermore, a wide passivation region was observed in the all PDP diagrams in the absence of chloride ions. Conversely, after the addition of 0.2 M NaCl to the 5 g/L citric acid solution, the corrosion behavior of the samples significantly changed, as shown in Fig. 9 b. According to the data in Table 4 , in the solution containing 0.2 M chloride, the E corr decreased and i corr negligibly increased with increasing plastic deformation for all samples except the 45% cold-worked sample. In the 45% cold-deformed sample, E corr was the nobler, and i corr was the lowest among all samples, indicating better corrosion resistance. Moreover, unlike the 0% and 15% cold-worked samples, which did not exhibit any passivation region, the 30% and 45% deformed samples showed considerable passive behavior. Table 4 E corr and i corr values extracted from the PDP curves in Fig. 9 Electrolyte Strain (%) i corr (A/cm 2 ) E corr (V) 5 g/L citric acid 0 1.53×10 − 7 0.071 15 1.37×10 − 7 0.011 30 1.10×10 − 7 -0.001 45 1.57×10 − 7 -0.104 5 g/L citric acid + 0.2 M NaCl 0 1.47×10 − 5 -0.385 15 2.38×10 − 5 -0.462 30 6.25×10 − 5 -0.514 45 8.63×10 − 6 -0.210 To investigate the corrosion damage on the sample surfaces, Fig. 10 displays SEM images showcasing the sample surfaces following the PDP test in 5 g/L citric acid + 0.2 M NaCl solution. As shown in Fig. 10 a, scattered pits are visible on the sample without plastic deformation, particularly in the α (dark) regions and interphase boundaries. However, in the cold-deformed samples, fewer pits are formed in the center of the cylindrical samples, where plastic deformation is more severe. According to Figs. 10 b and 10 c, as the plastic deformation increased, fewer corrosion pits formed in the center of the samples, while the side areas experienced more pitting corrosion. As shown in Fig. 10 d, in the 45% compressed sample, the pits were significantly reduced in number and became negligibly larger. Numerous studies have examined the effects of cold work on the microstructure of 2101 LDX. Cold plastic deformation in this steel, along with the formation of SIM in the γ phase, has been well documented 9 . Additionally, cold working increases the density of defects in both the α and γ phases 27 . This increase in defects, dislocations, and microstructural evolution also leads to a decrease in EWF in both phases of 2101 LDX, resulting in accelerated surface corrosion 17 . Furthermore, Wang et al. 28 reported that cold working in this steel triggers the precipitation of Cr 2 N phases and the formation of α' martensite in the γ phase. As mentioned in the previous sections, cold plastic deformation has led to the formation of SIM and dislocations density increasing, initially in the γ phase and subsequently in the α phase. Based on the results of electrochemical analysis and immersion tests, it can be concluded that the deformed surfaces are more sensitive to corrosion due to the higher density of defects and the presence of SIM and Cr 2 N phases. As Fig. 10 demonstrates, a more active surface facilitates faster protective layer formation from corrosion products, particularly within chloride-containing solutions. Similarly, studies on the effects of cold work on the corrosion of 304 and 316L stainless steels have also demonstrated that, despite the triggered corrosion reactions due to plastic deformation, the formation of a passive protective layer is stimulated by cold work, which generally enhances overall corrosion resistance 17 , 38 , 39 . The SEM images in Fig. 11 provide more detailed data on the corrosion of samples after the PDP test in 5 g/L citric acid + 0.2 M NaCl solution. Additionally, the results of EDS analysis for the areas specified in Fig. 11 are presented in Table 5 . As seen in Fig. 11 a, in the corroded sample after annealing, corrosion at the ferrite boundaries is visible, with numerous pits present at the α grain boundaries and γ/α interphase. However, as shown in Fig. 11 b and 11 c, with the increase in cold plastic deformation, grain boundary corrosion was significantly reduced compared to the as-annealed sample. According to the data in Table 5 , no significant changes in the chemical composition of the α phase (areas 1, 4, and 7) occurred due to cold plastic deformation. However, the γ phase showed higher chromium content after 30% and 45% deformation (regions 2, 5, and 8). This suggests that more chromium oxides formed on the surface of the γ phase, which were not dissolved in the electrolyte solution during the electrochemical test. Additionally, EDS analysis of the pits revealed an increase in Cr and Mn content after cold deformation in these areas. The higher nitrogen content in the pits, particularly in the 45% deformed sample, indicates that these pits formed preferentially near the Cr 2 N phases. The EDS-Map images in Fig. 12 further illustrate the distribution of elements in all corroded samples, showing higher concentrations of O and Cr in the pit areas. The distribution of Fe in the α and γ phases also indicates uniform surface corrosion. Table 5 EDS analysis results (At%) for the areas marked in Fig. 11 . Strain Area Region C N O Cr Mo Mn Fe Ni 15% 1 Ferrite 0.01 0.01 1.78 22.91 0.09 5.02 69.04 1.14 2 Austenite 0.01 0.01 2.17 20.59 0.1 5.48 69.85 1.79 3 Pit 0.01 0.38 2.66 24.57 0.01 7.14 64.18 1.05 30% 4 Ferrite 0.01 0.02 2.27 22.49 0.12 5.09 68.94 1.06 5 Austenite 0.02 0.02 1.47 21.35 0.1 5.39 70.34 1.31 6 Pit 0.02 0.45 2.26 27.1 0.01 8.76 60.61 0.79 45% 7 Ferrite 0.03 0.02 2.42 22.75 0.12 5.05 68.55 1.06 8 Austenite 0.01 0.02 1.47 21.35 0.1 5.39 70.35 1.31 9 Pit 0.04 1.99 1.95 28.97 0.03 8.72 58.07 0.23 In summary, according to the SEM and PDP results, increasing cold plastic strain resulted in less grain boundary corrosion in the ferrite phases. The higher density of dislocations created a more active surface, leading to more intense uniform corrosion and a faster formation of a protective layer. Additionally, the precipitation of Cr 2 N phases stimulated by cold deformation 40 , made these phases more susceptible to pit formation. The formation of SIM in the γ phase during cold working reduced the corrosion resistance of this phase compared to the as-annealed state. As the difference in corrosion resistance between the α and γ phases decreased, galvanic corrosion between these phases became slower. 3.4 EIS investigations To investigate the corrosion mechanism, EIS tests were conducted in the OCP. The samples were placed as working electrodes in the electrolyte solution for 24 hours until a stable OCP was achieved. The Nyquist plots in Fig. 13 illustrate the corrosion behavior of the samples, and the simulated parameters from the corresponding equivalent circuit are reported in Table 6 . The simulation error for each curve was estimated to be less than 3%. For the 15% and 30% cold-worked samples, an equivalent circuit similar to Fig. 14 (a) was used to simulate the EIS data consisting of a solution resistance (R 1 ) in series with a constant phase element (CPE)/charge transfer resistance (Q dl /R 2 ). In this circuit, R 1 represents the solution resistance, and R 2 corresponds to the charge transfer resistance at the 2101 LDX interface. For the 15% and 30% cold-worked samples, a second time-constant at high-frequency region appeared due to passive film formation also detected in the PDP plots (Fig. 14 (a)) 41 . The proposed equivalent circuit could be used when the surface films form uniform islands and the entire metal surface is not covered by the passive layer 42 . The CPE f and R f correspond to passive film capacitance and resistance, respectively. However, for the 45% cold-pressed sample, the circuit shown in Fig. 14 (b) was employed. In this arrangement, the entire surface of the metal is covered by the passive film. The CPE-P or n was also reported as a sign of the non-ideal capacitance behavior of passive film and surface electric double layer. The CPE was used instead of capacitance (C) due to the non-ideal nature of the surface. The surface heterogeneity could be originated from different reasons, especially surface roughness 43 . The ideal capacitance of the electric double layer and passive film was calculated according to Eq. 2 and Eq. 3 44,45 : C dl = Y 0, dl 1/ n . ( \(\:\frac{{R}_{s}{R}_{ct}}{{R}_{s}+{R}_{ct}}\) ) (1− n )/ n (2) C f = Y 0, f 1/n . R f (1− n )/ n (3) Table 6 Simulated equivalent circuit parameters based on the EIS data in Fig. 13 . (Cl-) Strain R f CPE f n R ct CPE dl n C dl C f W (%) Ω.cm 2 S.Ω −1 .cm − 2 Ω.cm 2 S.Ω −1 .cm − 2 F.cm − 2 F.cm − 2 ??? 0 0 - - - 2.96×10 4 4.51×10 − 5 0.859 - - - 0.01 - - - 2.84×10 4 5.12×10 − 5 0.836 - - - 0.2 - - - 5.76×10 3 7.18×10 − 5 0.839 - - - 15 474.4 7.94×10 − 4 0.728 2.91×10 5 1.23×10 − 4 0.873 4.80×10 − 5 1.09×10 − 2 - 30 110 1.67×10 − 3 0.801 1.81×10 5 1.18×10 − 4 0.827 2.84×10 − 5 6.68×10 − 3 - 45 1.8×10 3 1.80×10 − 6 0.788 1.45×10 3 9.78×10 − 5 0.894 4.99×10 − 5 1.72×10 − 5 4.21×10 − 5 According to the EIS data, a consistent pattern was observed for as-annealed LDX 2101 samples in the absence and presence of chloride ions. The corrosion behavior of the immersed sample is less affected by the low concentration of chloride ions. The observed negligible corrosion improvement in the presence of 0.01 molar Cl − anions could be due to iron-rich oxide and hydroxide formation enhanced by chloride ions (See section 3.5 ). However, severe corrosion occurred after the addition of 0.2 molar Cl − ions to the electrolyte. Also, the n values show a decreasing trend with the Cl − content of electrolyte. The n value is a sign of surface roughness 44 . Surface attack by the Cl − ions left behind a rough surface. The n value for an ideal capacitor is 1. The electric double layer on a rough surface shows a lower n value. After work hardening up to 30% strain the second relaxation time appeared could be due to intensive passive film formed on the nobler phases in the aforementioned galvanic couples like surface islands. The n values for samples with work hardening up to 30% strain are relatively lower than as-annealed samples due to the passive islands formation. Also, the charge transfer resistance is considerably larger than as-annealed samples. A notable increase in R ct was observed in the 15% and 30% cold-compressed samples, suggesting that cold work promoted the formation of the protective layer, likely due to the increased surface higher energy. This protective layer, formed during the 24-hour immersion period, significantly improved corrosion resistance in these samples. The reduction in the PREN difference of the two phases could be considered as a reason for these observations. In contrast, as shown in Fig. 14 (b), the corrosion behavior of LDX 2101 after 45% strain deviates from that of the other samples. In the sample with 45% strain, the surface arrangement was changed and full coverage of the steel surface occurred. With a considerable decrease in the PREN difference and disappearing galvanic effect, a relative barrier layer covers the entire surface of the metal. The large high-frequency phase angle values for the sample with 45% strain could be considered a sign of uniform barrier surface film formation 42 . The largest charge transfer and the lowest double-layer CPE are recorded for the sample with 45% strain proving the best protective behavior among all samples. Generally, charge transfer resistance is directly correlated with corrosion resistance, where a larger Nyquist curve diameter corresponds to better corrosion resistance 44 . The pitting corrosion reduction and impedance resistance improvement, due to the dislocation movement into the γ phases and consequent SIM formation, are the result of the corrosion study part which is explained in the next section with more details. 3.5 Corrosion Mechanism According to the characterization data and electrochemical analyses, the relationship between the microstructure and corrosion performance of LDX 2101, considering the presence or absence of chloride in the solution and the history of cold work, is schematically illustrated in Fig. 15 . Several researchers have reported that the passive film developed on stainless steels typically consists of two distinct layers. The inner layer is composed of Cr 2 O 3 , which serves as a p-type semiconductor, while the outer layer is composed of iron-rich oxide and hydroxide, functioning as an n-type semiconductor. The inner Cr 2 O 3 layer plays a critical role in corrosion resistance by providing robust protection against corrosion, while the outer iron-rich layer contributes to the overall stability of the passive film 13 , 46 – 49 . In citric acid solution, corrosion at the γ/α interface and the α grain boundaries primarily occurs due to the higher energy of the phase boundary and the relatively lower resistance of the α phase, attributed to its lower EWF. With the addition of Cl ꟷ to the acidic solution, pitting corrosion at phase boundaries and in the α phase becomes more pronounced, which is explained by its lower PREN. When cold strain is applied, dislocation movement is initiated, especially in the γ phase, due to cold plastic deformation, resulting in the formation of SIM in the γ phase. As the hardness of the γ phase significantly increases, deformation begins to occur in the α phase as well. The plastic deformation leads to the formation of SIM at the γ/α boundaries. Unlike γ and α phases, SIM regions are active and are more susceptible to corrosion 29 . This increased activity, combined with SIM formation, accelerates corrosion in the γ regions, bringing their resistance closer to that of the less noble α phase, which acts as the cathode, thus slowing the rate of galvanic corrosion and consequent pitting. Furthermore, as the dislocation density increases, the surface energy of both phases rises, promoting the faster formation of a protective layer, which enhances corrosion resistance. In the meantime, the Cr 2 N precipitates are preferential areas for pit formation due to chromium depletion around them. These precipitates, typically located at grain boundaries, increase susceptibility to chloride-induced corrosion in these regions. The addition of chlorine to the citric acid solution increases the corrosiveness of the electrolyte, making ferrite phases, grain boundaries, and Cr 2 N regions more susceptible to pitting corrosion. Chlorine compromises the protective passive layer, reducing its effectiveness. In contrast, cold working enhances the formation of the passive layer, thereby hindering the initiation and growth of pits. Overall, based on surface roughness measurements of the immersion samples and electrochemical test results, chlorine exacerbates the corrosion of the ferrite phase, whereas cold working improves resistance to pitting corrosion. A recent study by Assumpção et al. 50 demonstrated that the corrosion properties of 2304 LDX were significantly enhanced through cold rolling, which induced residual compressive stresses and reduced nucleation sites for corrosion pits in chlorine-rich media. However, martensitic transformation adversely affects corrosion resistance by creating microstructural inhomogeneities, such as α'-martensite/austenite interfaces. In our case study, the decrease in austenite corrosion resistance due to SIM has narrowed the gap between the corrosion resistances of austenite and ferrite, thereby mitigating galvanic corrosion by reducing the anodic and cathodic potential difference. 4 Conclusion In the present research, the effects of cold work and chloride/citric acid concentration on the corrosion properties of LDX 2101 were investigated. For this purpose, CV, PDP, and EIS electrochemical tests were conducted, and phase evolutions after cold work, as well as corrosion damage, were analyzed using SEM, XRD, AFM, and OM. The most important results of this research are as follows: LDX 2101 consists of γ and α phases, with Cr 2 N and M 23 C 6 precipitates also forming. Cr 2 N phases were observed along the α grain boundaries and at the α/γ interphase boundaries. Cold working in LDX 2101 initially deformed the γ phase, followed by the α phase at higher strains. The formation of SIM in the γ phase and the increase in dislocation density in both phases resulted in a 54.7 % increase in hardness for the γ phase and an 11% increase for the α phase after 45 % cold strain. Galvanic corrosion in LDX 2101 was observed in citric acid, where the corrosion resistance of the α phase was lower. With the addition of chloride to the solution, pitting corrosion occurred in the α phase and at grain boundaries, with Cr 2 N precipitates serving as preferred corrosion sites. High concentrations of chloride and citric acid intensified the corrosion of LDX 2101. According to the results of the immersion test and PDP data, cold work improved corrosion resistance in citric acid-chloride solutions. The faster formation of the protective layer in these samples, attributed to the increased density of dislocations and a more active surface, was the main reason for this improvement. Based on the EIS data, after 24 h of immersion, the as-annealed sample exhibited the lowest corrosion resistance in the chloride-citric acid solution. Additionally, corrosion resistance improved at strains of 15 % and 30%, and in the 45 % deformed sample, the corrosion mechanism changed due to the formation of SIM and increased dislocation density, which resulted in enhanced passive film protection. Declarations Author Contribution Mazdak Izadi and Saeid Karimi conceived of the presented idea, developed the theory, verified the analytical methods, supervised the findings of this work. All authors discussed the results and contributed to the final manuscript.Mohammadreza Mokhtare performed the experiments, derived the models and analysed the data, and wrote the manuscript. All authors discussed the results and contributed to the final manuscript. Data Availability All data generated and analyzed during this study are included in this article. References In the present research, the effects of cold work and chloride/citric acid concentration on the corrosion properties of LDX 2101 were investigated. For this purpose, CV, PDP, and EIS electrochemical tests were conducted, and phase evolutions after cold work, as well as corrosion damage, were analyzed using SEM, XRD, AFM, and OM. The most important results of this research are as follows: LDX 2101 consists of γ and α phases, with Cr 2 N and M 23 C 6 precipitates also forming. Cr 2 N phases were observed along the α grain boundaries and at the α/γ interphase boundaries. Cold working in LDX 2101 initially deformed the γ phase, followed by the α phase at higher strains. The formation of SIM in the γ phase and the increase in dislocation density in both phases resulted in a 54.7 % increase in hardness for the γ phase and an 11% increase for the α phase after 45 % cold strain. Galvanic corrosion in LDX 2101 was observed in citric acid, where the corrosion resistance of the α phase was lower. With the addition of chloride to the solution, pitting corrosion occurred in the α phase and at grain boundaries, with Cr 2 N precipitates serving as preferred corrosion sites. High concentrations of chloride and citric acid intensified the corrosion of LDX 2101. According to the results of the immersion test and PDP data, cold work improved corrosion resistance in citric acid-chloride solutions. The faster formation of the protective layer in these samples, attributed to the increased density of dislocations and a more active surface, was the main reason for this improvement. Based on the EIS data, after 24 h of immersion, the as-annealed sample exhibited the lowest corrosion resistance in the chloride-citric acid solution. Additionally, corrosion resistance improved at strains of 15 % and 30%, and in the 45 % deformed sample, the corrosion mechanism changed due to the formation of SIM and increased dislocation density, which resulted in enhanced passive film protection. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6483885","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":450841566,"identity":"f56af2f9-cc88-486e-9182-f77a3227721b","order_by":0,"name":"Mohammadreza Mokhtare","email":"","orcid":"","institution":"Hamedan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Mohammadreza","middleName":"","lastName":"Mokhtare","suffix":""},{"id":450841568,"identity":"a53d8717-ba97-4fe9-8ab2-179dfc9e6071","order_by":1,"name":"Mazdak Izadi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA90lEQVRIiWNgGAWjYJACCYYDDAxsIEZCBZBkZm4gRcsZkBZGIrWAGYxtIIqAFt324w9v/DjDIMfHf/jhjYfzaqP524FaflRsw6nF7ExCsmXPDQZjNoZjxhaJ247nzjjM2MDYc+Y2bi0HEo5J8HxgSGxjbDCTSNx2LLcBqIWZsQ2PlvMP2yT/fGCob2Nm/yaROOdY7nyCWm4ks0nz3GBIYGPjAdrSUJO7gbCWZ8zWMmckDNt4eIotEo4dyN0I1HIQr1/Opz+8+eaYjbx8//GNN3/U1OXOO3/44IMfFbi1QIEEjHEYTB4gpB4Z1JGieBSMglEwCkYIAAD6kFzJKY5xzgAAAABJRU5ErkJggg==","orcid":"","institution":"Hamedan University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Mazdak","middleName":"","lastName":"Izadi","suffix":""},{"id":450841569,"identity":"0ad0510a-0050-4999-81a6-9d601712dd80","order_by":2,"name":"Saeid Karimi","email":"","orcid":"","institution":"Hamedan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Saeid","middleName":"","lastName":"Karimi","suffix":""}],"badges":[],"createdAt":"2025-04-19 09:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6483885/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6483885/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81939811,"identity":"b9f2f47c-9eb7-4355-860d-c21645cdf622","added_by":"auto","created_at":"2025-05-05 06:48:55","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":102548,"visible":true,"origin":"","legend":"\u003cp\u003eEquilibrium phase diagram of LDX 2101 calculated using JMatPro software, based on the chemical composition shown in Table 1.\u003c/p\u003e","description":"","filename":"image1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/ab4bf94fe56b8ab4d7d16d4e.jpeg"},{"id":81939272,"identity":"346db6c2-317a-41fb-a94a-b3403e4822ed","added_by":"auto","created_at":"2025-05-05 06:40:55","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":256816,"visible":true,"origin":"","legend":"\u003cp\u003e(a): True stress-strain diagram for the cold compression test of LDX 2101 cylindrical samples, (b): Work hardening rate diagram alongside the OM image of the sample after heat treatment at 670 °C for 2 hours, (c): Vickers hardness of the samples after various strains and (d): Dislocation density diagram for the α and γ phases.\u003c/p\u003e","description":"","filename":"image2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/4043e70247fb5cd4f80f26b3.jpeg"},{"id":81937872,"identity":"1eb26d33-f7c4-46a1-a1de-23dd64891c03","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":132827,"visible":true,"origin":"","legend":"\u003cp\u003eXRD graph for samples after heat treatment at 670 °C for 2 h, showing different strains after the cold compression test.\u003c/p\u003e","description":"","filename":"image3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/face3045563593edcd07290e.jpeg"},{"id":81937873,"identity":"a62ddc0a-576e-4d9a-86ab-80d2231d148a","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":88350,"visible":true,"origin":"","legend":"\u003cp\u003eMicrohardness test results for annealed samples after cold plastic deformations.\u003c/p\u003e","description":"","filename":"image4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/8da91740d964ecc8654ae772.jpeg"},{"id":81940560,"identity":"298005f5-700a-4df6-bbcd-d2db3ab0224e","added_by":"auto","created_at":"2025-05-05 06:56:55","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":297690,"visible":true,"origin":"","legend":"\u003cp\u003eCV graphs for annealed LDX 2101 samples in different concentrations of citric acid and chloride at room temperature.\u003c/p\u003e","description":"","filename":"image5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/697406e95925d303419b52ed.jpeg"},{"id":81937878,"identity":"f846ec64-592e-4a79-8e21-9a0fb7bdd50a","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":879605,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the LDX 2101 microstructure: (a) Annealed sample after etching; images of samples after corrosion: (b) and (c) in 5 g/L citric acid solution; (d) after adding 0.01 M NaCl; (e) and (f) after the addition of 0.2 M NaCl; (g) and (h) magnification of pits marked in (d) and (e).\u003c/p\u003e","description":"","filename":"image6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/9ada40e5750e7ce034899738.jpeg"},{"id":81937879,"identity":"d50f8e0a-1733-4d31-afd7-7151207f4c60","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":116493,"visible":true,"origin":"","legend":"\u003cp\u003eMass changes observed upon immersion of samples in various electrolytes at room temperature over seven days: (a) impact of NaCl concentration and (b) the cold work effect.\u003c/p\u003e","description":"","filename":"image7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/ae8a347e12325fb856ae4cdd.jpeg"},{"id":81939812,"identity":"cad45f51-8342-452d-8cf5-2a7061579a99","added_by":"auto","created_at":"2025-05-05 06:48:55","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":221733,"visible":true,"origin":"","legend":"\u003cp\u003eAFM results for the α phase of 2101 LDX samples: (a) as-polished sample, and corroded surface after immersion in a solution of 5 g/L citric acid + 0.2 M NaCl for 7 days; (b): without plastic deformation, (c): after 15 % cold work, (d) after 30 % cold work, (e): after 45% cold work and (f): ferrite roughness values extracted from AFM data.\u003c/p\u003e","description":"","filename":"image8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/31419bc4de0aeb8efcb42719.jpeg"},{"id":81937885,"identity":"1152da66-330c-46a3-ad7d-36ea121e6129","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":115279,"visible":true,"origin":"","legend":"\u003cp\u003ePDP curves for deformed samples examined at room temperature: (a) 5 g/L citric acid solution and (b) 5 g/L citric acid solution with 0.2 M NaCl.\u003c/p\u003e","description":"","filename":"image9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/9738887cc86aecc123148238.jpeg"},{"id":81937891,"identity":"ab6d0248-e33d-47e8-a7d1-fc5b4d39fc18","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":777226,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the sample surfaces after the PDP test in 5 g/L citric acid and 0.2 M NaCl solution at room temperature.\u003c/p\u003e","description":"","filename":"image10.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/a876d1b0686cc6e4307598f5.jpeg"},{"id":81937900,"identity":"646dda22-d2d8-44ee-9fc1-57ceb55ba029","added_by":"auto","created_at":"2025-05-05 06:32:55","extension":"jpeg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":889206,"visible":true,"origin":"","legend":"\u003cp\u003eSEM micrographs of the corroded surfaces of samples with different strains after the PDP test in a 5 g/L citric acid + 0.2 M NaCl solution.\u003c/p\u003e","description":"","filename":"image11.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/3618b18fa7e4933572fb6705.jpeg"},{"id":81939276,"identity":"e0a2a107-cb2b-4aeb-9d28-6c0a3e2a60f0","added_by":"auto","created_at":"2025-05-05 06:40:55","extension":"jpeg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":1304785,"visible":true,"origin":"","legend":"\u003cp\u003eEDS-Map results for the samples after the PDP test (a): as-treated sample corroded at 5 g/L citric acid solution + 0.01 M NaCl, and samples corroded in 5 g/L citric acid + 0.2 M NaCl: (b) Undeformed, (c) 15 % cold-compressed, (d) 30 % cold-compressed, and (e) 45 % cold-compressed samples.\u003c/p\u003e","description":"","filename":"image12.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/b2170c852c9618f85461eaa1.jpeg"},{"id":81939290,"identity":"b26fdc1e-a9b4-43fa-b55c-08306f9422bc","added_by":"auto","created_at":"2025-05-05 06:40:55","extension":"jpeg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":217700,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Nyquist curves for LDX 2101 after annealing heat treatment at OCP in a 5 g/L citric acid solution and 5 g/L citric acid solutions with the addition of 0.01 M and 0.2 M NaCl; (b) and (c) Bode curves corresponding to Fig. 13(a); (d) Nyquist curves for cold-worked samples in a 5 g/L citric acid + 0.2 M NaCl solution; and (e) and (f) the corresponding Bode curves.\u003c/p\u003e","description":"","filename":"image13.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/4f8bf28a867d99bfba81791d.jpeg"},{"id":81939817,"identity":"1b37e421-a7af-4029-9474-0570e447b1cc","added_by":"auto","created_at":"2025-05-05 06:48:55","extension":"jpeg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":91467,"visible":true,"origin":"","legend":"\u003cp\u003eEquivalent electric circuits for (a) 15 and 30% cold-worked sample and (b): for 45% cold-pressed sample.\u003c/p\u003e","description":"","filename":"image14.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/71d81eb61673010c0a574abc.jpeg"},{"id":81939820,"identity":"20d0f116-1de7-43b2-89df-00da1493a912","added_by":"auto","created_at":"2025-05-05 06:48:55","extension":"jpeg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":216362,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the corrosion behavior of LDX 2101 in citric acid solution, highlighting the effects of cold plastic deformation and the presence/absence of chlorine in the electrolyte solution.\u003c/p\u003e","description":"","filename":"image15.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/70119bbd8e96fd4166aac552.jpeg"},{"id":82613983,"identity":"89bb54e1-87f7-4805-8ff0-82b70c131558","added_by":"auto","created_at":"2025-05-13 11:23:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6649359,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6483885/v1/ff9ef3b1-349f-42d3-877c-df5a1829d319.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Combined Effect of Cold Work and Chloride Content on Corrosion Mechanism of 2101 Lean Duplex Stainless Steel in Citric Acid","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eDuplex stainless steels (DSS) are a family of steels known as two-phase due to their structure, which consists of austenite (γ) with a face-centered cubic (FCC) crystal structure and ferrite (α) with a body-centered cubic (BCC) crystal structure \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Traditional stainless steels, such as 304 and 316L have been replaced by DSS due to their superior mechanical properties and excellent corrosion resistance \u003csup\u003e\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Lean duplex stainless steels (LDX) are a subset of the duplex stainless-steel family. By reducing expensive elements like Ni and Mo and adding γ-stabilizer elements such as Mn and N to the chemical composition, LDX are not only more economical but also have fewer harmful phases, such as σ and χ, due to their lower alloying elements \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Furthermore, the addition of N in LDX improves both the corrosion resistance and strength/formability. The most important representatives of LDX include 2101 LDX, SAF 2304, and AL 2003 \u003csup\u003e7\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eLDX 2101 is an economical two-phase stainless steel with lower Ni and Mo content, offering corrosion properties similar to those of commercial single-phase or two-phase stainless steels \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. This steel is designed to form less martensite in γ and exhibits uniform corrosion properties superior to those of grade 304 stainless steel, with localized corrosion resistance comparable to that of 316L. It also offers better chloride stress corrosion cracking resistance than austenitic steels, including 304, making it a suitable substitute for these stainless steels \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Based on transmission electron microscope (TEM) investigations, in addition to the α and γ phases, Cr₂N and Cr₂₃C₆ phases are also formed in LDX 2101 \u003csup\u003e10\u003c/sup\u003e. Due to the absence of Mo and the high percentage of N, the formation of nitride phases in LDX 2101 creates areas that are sensitive to pitting corrosion \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Additionally, in LDX 2101, the α-phase exhibits lower corrosion resistance, making it more susceptible to both galvanic and pitting corrosion. \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Nevertheless, the formation of a passive layer protects the surface of LDX 2101 against corrosion, even in harsh chloride environments \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Additionally, due to the presence of N, the γ phase forms a better protective layer, making LDX 2101 resistant to pitting corrosion in chloride environments at temperatures below 10\u0026deg;C \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOne of the most important post-process fabrication methods for producing metal parts and tools is cold plastic deformation, which influences the final properties of steels \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. LDX 2101 is a transformation-induced plasticity (TRIP) steel that offers varying mechanical properties depending on the γ/α phase fraction \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. According to Fuertes et al. \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, cold plastic deformation in LDX 2101 induces the formation of martensite and mechanical twins in the γ phase. In another study by Zhang et al. \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, it was reported that cold work primarily causes dislocation slip in the α phase, leading to the formation of dislocation cells and deformation microbands. On the other hand, in the γ phase, strain-induced martensite (SIM) and twinning are observed \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eLDX 2101 is used in the food industry due to its superior corrosion resistance and cost-effectiveness and exhibits better corrosion behavior compared to 430 and 316L steels in the environments of the whey and dairy industries \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Among the organic acids found in the food industry, citric acid is particularly corrosive and is present in foods such as tomatoes and lemons \u003csup\u003e\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. According to Mazinanian et al. \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, the rate of metal release due to corrosion in LDX 2101 in tap water and citric acid environments at temperatures of 40\u0026deg;C and 70\u0026deg;C meets the Council of Europe standards. This makes LDX 2101 a leading candidate for use in the food industry.\u003c/p\u003e \u003cp\u003eBased on the literature review and the applications of LDX 2101 in the food industry, this study aims to address this gap by systematically investigating the influence of cold work and varying concentrations of chloride/citric acid on the corrosion behavior of LDX 2101. For this purpose, detailed electrochemical investigations and immersion tests were conducted. Surface evolutions after corrosion were examined using optical microscopy (OM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Cold compression testing, work hardening rate assessment, macro and microhardness testing, and X-ray diffraction (XRD) analysis were performed. This research provides a better understanding of the working process and conditions for using LDX 2101 in the food industry and its post-fabrication processes.\u003c/p\u003e"},{"header":"2 Materials and method","content":"\u003cp\u003eThe rolled and annealed ingot of LDX 2101 stainless steel with a thickness of 9 mm and chemical composition detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e was prepared. The phase diagram of the alloy was calculated using JMatPro software based on the chemical composition from Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. To achieve a 50\u0026ndash;50 phase fraction of α and γ, the rolled and annealed ingot was heat-treated at 670\u0026deg;C for 2 h and then cooled in air. Nine samples, each with dimensions of 9\u0026times;10\u0026times;10 mm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, and six cylindrical samples with a diameter of 5 mm and a height of 9 mm were prepared using a wire-cutting method. The surface of the samples was chosen to be perpendicular to the rolling direction to investigate the properties. To apply plastic deformation to the cylindrical samples, cold compression tests were conducted using a Santam STM50 machine at a strain rate of 0.01 s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Strains of 15%, 30%, and 45% were applied to the samples, which were then cut diagonally in half from the middle using a wire cutter for further investigation. The surfaces of the samples were prepared using sandpaper ranging from 80 to 3000 mesh, followed by polishing with a nano-alumina solution. For metallography, the samples were electrolytically etched using a solution of 50 g/L KCl in distilled water, with the samples acting as the anode under a voltage of 5 V for 10 s.\u003c/p\u003e \u003cp\u003eThe Vickers hardness of the samples was measured using a universal testing device with a force of 980 N and a dwell time of 15 s. Additionally, the Vickers microhardness of each phase was examined using a Koopa MH4 machine with a force of 1 N and a 15-second dwell time. In the hardness tests, five measurements were taken for each sample/phase, and the average results were reported.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical Composition (wt%) of LDX 2101 Investigated in This Research\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePercentage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eBase.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo investigate the corrosion properties of the samples, solutions of 5 and 50 g/L citric acid with 0, 0.01, and 0.2 M NaCl were prepared. A concentration of 5 g/L of citric acid is considered standard in the food industry \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Cyclic Voltammetry (CV), Potentiodynamic Polarization (PDP), and Electrochemical Impedance Spectroscopy (EIS) tests were conducted using radstat200 machine to assess the corrosion properties of the samples in different solutions and at different strain levels. All electrochemical tests were conducted in a common three-electrode cell (counter electrode: Platinum, Reference electrode: Ag/AgCl). Before performing the corrosion tests, in the CV analysis, the samples were immersed in solutions with varying citric acid and NaCl concentrations for 2 h to reach a stable open circuit potential (OCP). For the PDP test on the strained samples, this time was extended to 24 h to ensure a stable OCP. The EIS measurements were done in the frequency range of 100000 Hz to 0.1 Hz at OCP. The sinusoidal stimulus potential was 0.01 V. Additionally, an immersion test was performed on undeformed samples in three solutions: 5 g/L citric acid, and 5 g/L citric acid with 0.01 and 0.2 M NaCl for one week. For the 15%, 30%, and 45% cold-worked samples, the immersion test was conducted in a solution of 0.2 M NaCl and 5 g/L citric acid for 168 h. Mass changes during the immersion test were measured using an A\u0026amp;D GR-200 scale with an accuracy of 0.0001 grams. To examine the phase evolutions of the samples after cold work, X-ray diffraction (XRD) tests were performed using a Panalytical PW3050 device equipped with a Cu cathode. Optical microscope (OM) images were captured using a Dewinter DG-VICTORY microscope. For surface examination, an FEI Quanta 200 scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) probe was used. Additionally, a BRISK atomic force microscope (AFM) was employed to assess the surface morphology and roughness of the α phase after being corroded in the immersion test.\u003c/p\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Microstructural evolutions after cold work\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the equilibrium phase diagram of LDX 2101 simulated using JMatPro software. As illustrated, this stainless steel consists of two main phases, α, and γ, whose fractions vary according to the heat treatment temperature. However, at temperatures of 670\u0026deg;C and 1130\u0026deg;C, the fraction of these two phases is equal. In addition to the α and γ phases, the formation of M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e carbides and M\u003csub\u003e2\u003c/sub\u003eN nitrides, both rich in chromium, is predicted in this alloy. The prediction results from Thermo-Calc software similarly indicate the presence of α, γ, chromium-rich carbides, and nitride phases with the same phase fraction, consistent with the JMatPro predictions \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Although there is a possibility of spinodal decomposition in DSSs with 21% chromium and above, a temperature of 670\u0026deg;C was chosen to achieve a structure with an equal phase fraction of α and γ, because spinodal transformation does not occur in LDX 2101 at temperatures above 600\u0026deg;C \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows the true stress-strain diagram for the cold compression test. Based on the linear region of elastic deformation, the compressive yield stress of 578 MPa was obtained for LDX 2101. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb illustrates that the rate of work hardening is extremely rapid up to a strain of approximately 11%. Beyond this strain, work hardening occurs at a relatively constant rate due to cold deformation. The hardness test results in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec indicate a significant increase in hardness due to cold work, with a 152% increase after 45% strain. However, the rate of hardness increase does not match the rate of strain hardening, suggesting the influence of other factors on hardness. It is noteworthy that LDX 2101 has a two-phase structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) consisting of α and γ. These two phases exhibit different strengths and hardness, and due to the difference in plasticity between the BCC and FCC crystal structures, work hardening occurs differently in these phases.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo investigate the effects of cold work on each phase, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed presents the dislocation density diagram for the α and γ phases, calculated using the Williamson-Hall \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e relationship based on the XRD data shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. As observed, cold work consistently increases the dislocation density in the γ phase, whereas the dislocation density in the α phase increases at a lower rate and shows minimal change, even in the strain range of 15\u0026ndash;30%. Similarly, it has been reported that during the cold deformation of LDX 2101, the γ phase experienced more deformation in cold rolling. Generally, the γ phase, with its FCC crystal structure, is softer and more plastically deformable than the BCC α phase at room temperature \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBased on the literature review, the formation of SIM in LDX 2101 due to the cold work has been reported. Unfortunately, it is not possible to detect martensite by the usual methods like SEM due to the non-diffusive nature of this transformation. Additionally, the crystal structure of martensite is BCC, with a lattice parameter very close to the α phase \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Based on the XRD graphs in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, as the strain level increases, the diffraction peak intensity of γ (200) decreases, and the α (200) increases. This observation may be associated with the transformation of γ to α\u0026prime;-martensite \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. The peaks related to Cr\u003csub\u003e2\u003c/sub\u003eN were also observed with increasing strain. However, due to the small phase fraction of these phases (less than 2 wt. %, as predicted by JMatPro), they are not detectable by XRD.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo better investigate strain-induced phase transformations, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the microhardness test results for the α and γ phases after cold working, taken from the central regions of cylindrical samples. As observed, in the annealed sample, the hardness of the α phase is higher than that of the γ phase. However, after cold working, the hardness of the γ phase increases significantly, while the α phase becomes slightly harder only after 45% strain. The increase in hardness of the γ phase can be attributed to two main factors: first, the increase in dislocation density, which increases the hardness of this phase; and second, the formation of SIM in γ, which significantly contributes to the hardness. According to Bassani et al. \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, the utilization of EBSD analysis in LDX 2101 revealed that hardness increment due to the work hardening occurred up to a 20% strain caused by cold working. Once the strain exceeds 20%, the formation of α\u0026prime;-martensite becomes the main factor contributing to the strength increase. Moreover, Chen et al. \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e reported that α\u0026prime;-martensite formed after multiple shot peening of SAF 2507 DSS, with approximately 31.6% α\u0026prime;-martensite observed on the impacted surface of the triply peened specimen.\u003c/p\u003e \u003cp\u003eHowever, according to Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, the hardness of the sample after 45% strain (380 HV) is higher than that of both the α and γ phases. This suggests the influence of additional factors on hardness increase, such as the Hall-Petch effect \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e and the formation of Cr\u003csub\u003e2\u003c/sub\u003eN phases, which are discussed in the following sections.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Effects of Cl/Citric Acid on Corrosion Properties\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the CV diagrams for the annealed sample of LDX 2101, exposed to 5 and 50 g/L citric acid with 0, 0.01, and 0.2 M NaCl at room temperature. The extracted data from the curves in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, including corrosion potential (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e), corrosion current density (\u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e), pitting corrosion protection potential (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epp\u003c/em\u003e\u003c/sub\u003e), and the pit nucleation resistance (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epn\u003c/em\u003e\u003c/sub\u003e=\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epp\u003c/em\u003e\u003c/sub\u003e-\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e) are reported in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. As seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, in non-chloride solutions, no hysteresis loop is observed, indicating that pitting corrosion does not occur in the citric acid solution. According to the data in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, increasing the concentration of citric acid results in a decrease in \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e and an increase in \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e, indicating lower resistance to uniform corrosion and faster kinetics at higher acid concentrations \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Additionally, images of the corroded sample surfaces in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed show no pits, only preferential corrosion of the α phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, after the addition of 0.01 M NaCl, the corrosion mechanism changes, and pitting corrosion was observed in all samples. Generally, increasing the chloride concentration from 0.01 M to 0.2 M, significantly reduced the pitting corrosion resistance. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the resistance to pit nucleation decreases with increasing chloride and citric acid concentrations. A noteworthy observation is the combined effect of high concentrations of chlorine and citric acid on pitting corrosion resistance. As both concentrations increase, the pitting resistance decreases significantly, as evident from the corroded surface after the CV test (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). However, in the 50 g/L citric acid solution, the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e in the 0.2 M NaCl solution is slightly higher compared to 0.01 M. The worst values of \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epn\u003c/em\u003e\u003c/sub\u003e were recorded for the 50 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution, highlighting a critical reduction in pitting corrosion resistance. The pit repassivation is observed for 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.01 M NaCl, 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl, and 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl samples. However, the repassivation process is disrupted in the 50 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution due to the increase corrosivity of the electrolyte and the destructive effect of chloride ions.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrosion parameters extracted from the CV diagrams of Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e after 2 h of immersion at room temperature.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003esolution\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e (A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e (V)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epp\u003c/em\u003e\u003c/sub\u003e (V)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003epn\u003c/em\u003e\u003c/sub\u003e (V)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCitric Acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNaCl\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e5 g/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.00 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.05\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.01 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.61\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.418\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.349\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.767\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.20 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.74\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.463\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.576\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e50 g/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.00 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.28\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.369\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.01 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.40\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.382\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.336\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.718\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.20 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.92\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.374\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.349\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo gain a deeper understanding of the corrosion process in samples treated with varying concentrations of citric acid and NaCl, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e displays the microstructure of the corroded surface of annealed LDX 2101. The results of EDS analysis of the areas marked in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e are also reported in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. As seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, in the etched sample of LDX 2101 after heat treatment, the two-phase microstructure is evident. According to the data in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the α phase is richer in Cr, while the γ phase contains higher amounts of Mn and N. This is due to the gamma-genic nature of Mn and N, which, unlike Cr, have a greater tendency to dissolve in γ. The Pitting Resistance Equivalent Number (PREN) is a constant for each alloy or phase, calculated according to Eq.\u0026nbsp;1 for low-Ni and high-Mn/N steels based on their chemical composition \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. The lower the PREN values, the lower the pitting corrosion resistance. According to the information in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the PREN number for the α phase is lower than that for the γ phase (23.39 vs. 24.19), indicating that this phase is less resistant to pitting corrosion.\u003c/p\u003e \u003cp\u003ePREN= %Cr\u0026thinsp;+\u0026thinsp;3.3\u0026times;%Mo\u0026thinsp;+\u0026thinsp;16\u0026times;%N (1)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEDS analysis (At. %) of the areas marked in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"12\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCondition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ephase\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c2\" namest=\"c1\" rowspan=\"2\"\u003e \u003cp\u003eAs etched\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e5.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e70.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e5.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e71.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"7\" rowspan=\"8\"\u003e \u003cp\u003eCitric acid 5 g/L\u0026thinsp;+\u0026thinsp;NaCl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.00 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e23.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e67.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e21.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e67.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e0.01 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e23.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e67.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e68.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.66\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e21.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e68.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.20 M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e23.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e68.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e20.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e5.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e69.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e28.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e8.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e60.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCr\u003csub\u003e2\u003c/sub\u003eN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e35.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e4.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e54.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, no pits were observed in the microstructure of the sample corroded in 5 g/L citric acid solution. However, the α regions and α grain boundaries were more severely damaged by corrosion. As shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef, Cr\u003csub\u003e2\u003c/sub\u003eN precipitates formed at the grain boundary regions and the phase boundaries between α and γ. The EDS-11 data in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows that these phases are rich in Cr and N. These areas create corrosion-sensitive sites due to Cr depletion from the matrix, leading to lower corrosion resistance of the grain boundary regions. Additionally, grain boundaries are high-energy regions, making them more susceptible to corrosion \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. According to the EDS analysis of areas 3 and 4, the surface corroded in citric acid solution showed low amounts of O, and the Cr content in the α phase increased slightly, suggesting the formation of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e oxides on the surface. With the addition of 0.01 M NaCl to the citric acid solution (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg), pits formed scattered throughout the α phases and at the interphase boundaries. Corrosion of the α boundaries was also observed. The chemical composition of area 7, which contains larger amounts of N, suggests pit formation in Cr\u003csub\u003e2\u003c/sub\u003eN areas. However, based on the EDS data from areas 5 and 6, the chemical composition of the surface after corrosion in citric acid with chloride does not differ significantly from that in citric acid alone. Increasing the NaCl concentration to 0.2 M led to more intense pit formation, as seen in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eh, with pits often occurring at α grain boundaries. The EDS analysis of areas 8 and 9 shows that the chemical composition of the corroded surface in both α and γ phases is similar, while the pits (marked as area 10) exhibit a significant increase in Cr and Mn. Additionally, the N content is highest in this area compared to others, indicating that nitrides are preferential sites for pitting corrosion.\u003c/p\u003e \u003cp\u003eOther studies on the corrosion of 2101 LDX in chloride environments have reported similar findings. The α phase has a low solubility for N, and this element has a high diffusion coefficient in the BCC matrix of the α phase, resulting in the formation of Cr\u003csub\u003e2\u003c/sub\u003eN phases. These phases tend to form at the α grain boundaries or the α/γ interfaces, creating sensitive sites for pitting corrosion in chloride solutions \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, in the presence of citric acid, the CV test results and SEM data indicate that the protective layer has been compromised due to the acidic environment. The absence of passive areas in the CV curves and the low percentage of O on the surfaces suggest that metal oxides are not stable under these conditions. Additionally, higher concentrations of the acid-chloride solution create more severe corrosion conditions. Therefore, it can be concluded that annealed 2101 LDX is effective only in environments with low concentrations of chlorine and citric acid across various industries.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Effects of cold strain on corrosion\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e presents the mass change of all samples vs. time during the weight-loss test, recorded at room temperature. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea, minimal corrosion occurred over 168 h in the 5 g/L citric acid solution, whereas the addition of chloride significantly increased the rate of weight loss. The primary reason for the reduction in specific mass is the corrosion progress, dissolution, and instability of corrosion products on the metallic surface, which is most intense during the first 50 h, and then gradually slows over time. The immersion test results align with the CV test, further confirming the destructive effect of chloride, especially at high concentrations.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo investigate the effects of cold work on the corrosion of annealed 2101 LDX, the immersion test was conducted under harsh conditions in a solution of 5 g/L citric acid and 0.2 M NaCl. The results of the specific mass changes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb. It is evident that strain increasing significantly reduces weight loss due to corrosion. For duplex stainless steel, overall corrosion resistance is influenced by the resistance of the weaker phase. Therefore, higher overall corrosion resistance can be achieved when the corrosion resistance of both phases is closely matched \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAccording to Guo et al. \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, after investigating the corrosion of 2101 LDX in a chloride environment using Scanning Kelvin Probe Force Microscopy (SKPFM), galvanic corrosion occurs between the α and γ phases, with the α phase experiencing more corrosion due to its lower electron work function (EWF). EWF, defined as the minimum energy required to remove an electron from a surface, indicates that a region with a higher EWF, which has a cathodic potential, exhibits better corrosion resistance compared to a region with a lower EWF, which has an anodic potential. Under similar conditions, the phase with the lower EWF is more susceptible to preferential corrosion \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. In addition to the lower resistance of the α phase in galvanic corrosion, as evidenced by SEM and OM data, this phase is also more susceptible to pitting corrosion due to its lower PREN. Considering all these factors, the AFM analysis results of the α phase after 168 h of immersion are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e to further investigate the corrosion behavior. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the as-polished sample displays minimal surface roughness, while the α phase in the sample corroded in a 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution for 7 days exhibits the highest surface roughness, indicating a more damaged surface. Notably, the surface roughness of the α phase decreases with increasing strain, which is associated with the reduced corrosion of this phase, a finding that is also confirmed by the immersion data.\u003c/p\u003e \u003cp\u003eTo investigate the effect of cold plastic deformation on corrosion properties, PDP tests were conducted on samples subjected to cold strain and immersed for 24 h in a 5 g/L citric acid and 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution. The results are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, and the extracted corrosion data (\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e) related to PDP graphs are reported in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, the increase in cold strain generally led to a decrease in corrosion resistance in the 5 g/L citric acid solution. According to the data in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, in the chloride-free solution, the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e steadily decreased with increasing cold work. Additionally, except for the 45% cold-worked sample, two other samples exhibited a negligible decrease in \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e. Thus, it can be concluded that corrosion resistance in the 5 g/L citric acid is not considerably affected by cold work. Furthermore, a wide passivation region was observed in the all PDP diagrams in the absence of chloride ions. Conversely, after the addition of 0.2 M NaCl to the 5 g/L citric acid solution, the corrosion behavior of the samples significantly changed, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb. According to the data in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, in the solution containing 0.2 M chloride, the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e decreased and \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e negligibly increased with increasing plastic deformation for all samples except the 45% cold-worked sample. In the 45% cold-deformed sample, \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e was the nobler, and \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e was the lowest among all samples, indicating better corrosion resistance. Moreover, unlike the 0% and 15% cold-worked samples, which did not exhibit any passivation region, the 30% and 45% deformed samples showed considerable passive behavior.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e values extracted from the PDP curves in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElectrolyte\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStrain (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e (A/cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ecorr\u003c/em\u003e\u003c/sub\u003e (V)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e5 g/L citric acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.53\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.071\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.37\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.011\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.10\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.57\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.104\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e1.47\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.385\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e2.38\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.462\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e6.25\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.514\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e8.63\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.210\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo investigate the corrosion damage on the sample surfaces, Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e displays SEM images showcasing the sample surfaces following the PDP test in 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea, scattered pits are visible on the sample without plastic deformation, particularly in the α (dark) regions and interphase boundaries. However, in the cold-deformed samples, fewer pits are formed in the center of the cylindrical samples, where plastic deformation is more severe. According to Figs.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003eb and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec, as the plastic deformation increased, fewer corrosion pits formed in the center of the samples, while the side areas experienced more pitting corrosion. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ed, in the 45% compressed sample, the pits were significantly reduced in number and became negligibly larger.\u003c/p\u003e \u003cp\u003eNumerous studies have examined the effects of cold work on the microstructure of 2101 LDX. Cold plastic deformation in this steel, along with the formation of SIM in the γ phase, has been well documented \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Additionally, cold working increases the density of defects in both the α and γ phases \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. This increase in defects, dislocations, and microstructural evolution also leads to a decrease in EWF in both phases of 2101 LDX, resulting in accelerated surface corrosion \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Furthermore, Wang et al. \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e reported that cold working in this steel triggers the precipitation of Cr\u003csub\u003e2\u003c/sub\u003eN phases and the formation of α' martensite in the γ phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs mentioned in the previous sections, cold plastic deformation has led to the formation of SIM and dislocations density increasing, initially in the γ phase and subsequently in the α phase. Based on the results of electrochemical analysis and immersion tests, it can be concluded that the deformed surfaces are more sensitive to corrosion due to the higher density of defects and the presence of SIM and Cr\u003csub\u003e2\u003c/sub\u003eN phases. As Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e demonstrates, a more active surface facilitates faster protective layer formation from corrosion products, particularly within chloride-containing solutions. Similarly, studies on the effects of cold work on the corrosion of 304 and 316L stainless steels have also demonstrated that, despite the triggered corrosion reactions due to plastic deformation, the formation of a passive protective layer is stimulated by cold work, which generally enhances overall corrosion resistance \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe SEM images in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e provide more detailed data on the corrosion of samples after the PDP test in 5 g/L citric acid\u0026thinsp;+\u0026thinsp;0.2 M NaCl solution. Additionally, the results of EDS analysis for the areas specified in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e are presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. As seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea, in the corroded sample after annealing, corrosion at the ferrite boundaries is visible, with numerous pits present at the α grain boundaries and γ/α interphase. However, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb and \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ec, with the increase in cold plastic deformation, grain boundary corrosion was significantly reduced compared to the as-annealed sample.\u003c/p\u003e \u003cp\u003eAccording to the data in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, no significant changes in the chemical composition of the α phase (areas 1, 4, and 7) occurred due to cold plastic deformation. However, the γ phase showed higher chromium content after 30% and 45% deformation (regions 2, 5, and 8). This suggests that more chromium oxides formed on the surface of the γ phase, which were not dissolved in the electrolyte solution during the electrochemical test. Additionally, EDS analysis of the pits revealed an increase in Cr and Mn content after cold deformation in these areas. The higher nitrogen content in the pits, particularly in the 45% deformed sample, indicates that these pits formed preferentially near the Cr\u003csub\u003e2\u003c/sub\u003eN phases. The EDS-Map images in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e further illustrate the distribution of elements in all corroded samples, showing higher concentrations of O and Cr in the pit areas. The distribution of Fe in the α and γ phases also indicates uniform surface corrosion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEDS analysis results (At%) for the areas marked in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStrain\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRegion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e15%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e69.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e20.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e69.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e24.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e7.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e64.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e30%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e68.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e21.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e70.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e27.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e8.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e60.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e45%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e22.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e68.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAustenite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e21.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e5.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e70.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e28.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e8.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e58.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn summary, according to the SEM and PDP results, increasing cold plastic strain resulted in less grain boundary corrosion in the ferrite phases. The higher density of dislocations created a more active surface, leading to more intense uniform corrosion and a faster formation of a protective layer. Additionally, the precipitation of Cr\u003csub\u003e2\u003c/sub\u003eN phases stimulated by cold deformation \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e, made these phases more susceptible to pit formation. The formation of SIM in the γ phase during cold working reduced the corrosion resistance of this phase compared to the as-annealed state. As the difference in corrosion resistance between the α and γ phases decreased, galvanic corrosion between these phases became slower.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 EIS investigations\u003c/h2\u003e \u003cp\u003eTo investigate the corrosion mechanism, EIS tests were conducted in the OCP. The samples were placed as working electrodes in the electrolyte solution for 24 hours until a stable OCP was achieved. The Nyquist plots in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e illustrate the corrosion behavior of the samples, and the simulated parameters from the corresponding equivalent circuit are reported in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The simulation error for each curve was estimated to be less than 3%.\u003c/p\u003e \u003cp\u003eFor the 15% and 30% cold-worked samples, an equivalent circuit similar to Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e(a) was used to simulate the EIS data consisting of a solution resistance (R\u003csub\u003e1\u003c/sub\u003e) in series with a constant phase element (CPE)/charge transfer resistance (Q\u003csub\u003edl\u003c/sub\u003e/R\u003csub\u003e2\u003c/sub\u003e). In this circuit, R\u003csub\u003e1\u003c/sub\u003e represents the solution resistance, and R\u003csub\u003e2\u003c/sub\u003e corresponds to the charge transfer resistance at the 2101 LDX interface. For the 15% and 30% cold-worked samples, a second time-constant at high-frequency region appeared due to passive film formation also detected in the PDP plots (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e(a)) \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. The proposed equivalent circuit could be used when the surface films form uniform islands and the entire metal surface is not covered by the passive layer \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. The CPE\u003csub\u003ef\u003c/sub\u003e and R\u003csub\u003ef\u003c/sub\u003e correspond to passive film capacitance and resistance, respectively. However, for the 45% cold-pressed sample, the circuit shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e(b) was employed. In this arrangement, the entire surface of the metal is covered by the passive film. The CPE-P or n was also reported as a sign of the non-ideal capacitance behavior of passive film and surface electric double layer. The CPE was used instead of capacitance (C) due to the non-ideal nature of the surface. The surface heterogeneity could be originated from different reasons, especially surface roughness \u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. The ideal capacitance of the electric double layer and passive film was calculated according to Eq.\u0026nbsp;2 and Eq.\u0026nbsp;3 \u003csup\u003e44,45\u003c/sup\u003e:\u003c/p\u003e \u003cp\u003e \u003cem\u003eC\u003c/em\u003e \u003csub\u003edl\u003c/sub\u003e = \u003cem\u003eY\u003c/em\u003e\u003csub\u003e0, dl\u003c/sub\u003e\u003csup\u003e1/\u003cem\u003en\u003c/em\u003e\u003c/sup\u003e. (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{{R}_{s}{R}_{ct}}{{R}_{s}+{R}_{ct}}\\)\u003c/span\u003e\u003c/span\u003e) \u003csup\u003e(1\u0026minus;\u003cem\u003en\u003c/em\u003e)/\u003cem\u003en\u003c/em\u003e\u003c/sup\u003e (2)\u003c/p\u003e \u003cp\u003e \u003cem\u003eC\u003c/em\u003e \u003csub\u003ef\u003c/sub\u003e = \u003cem\u003eY\u003c/em\u003e\u003csub\u003e0, f\u003c/sub\u003e \u003csup\u003e1/n\u003c/sup\u003e. \u003cem\u003eR\u003c/em\u003e\u003csub\u003ef\u003c/sub\u003e \u003csup\u003e(1\u0026minus;\u003cem\u003en\u003c/em\u003e)/\u003cem\u003en\u003c/em\u003e\u003c/sup\u003e (3)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSimulated equivalent circuit parameters based on the EIS data in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(Cl-)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStrain\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eR\u003csub\u003ef\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCPE\u003csub\u003ef\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eR\u003csub\u003ect\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCPE\u003csub\u003edl\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eC\u003csub\u003edl\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eC\u003csub\u003ef\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eW\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eΩ.cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eS.Ω\u003csup\u003e\u0026minus;1\u003c/sup\u003e.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eΩ.cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eS.Ω\u003csup\u003e\u0026minus;1\u003c/sup\u003e.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eF.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eF.cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e???\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.96\u0026times;10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.51\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.859\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.84\u0026times;10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5.12\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.836\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.76\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.18\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.839\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e474.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.94\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.728\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.91\u0026times;10\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.23\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4.80\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.09\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.67\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.801\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.81\u0026times;10\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.18\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.827\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.84\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6.68\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.8\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.80\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.788\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.45\u0026times;10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9.78\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.894\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4.99\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.72\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e4.21\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAccording to the EIS data, a consistent pattern was observed for as-annealed LDX 2101 samples in the absence and presence of chloride ions. The corrosion behavior of the immersed sample is less affected by the low concentration of chloride ions. The observed negligible corrosion improvement in the presence of 0.01 molar Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e anions could be due to iron-rich oxide and hydroxide formation enhanced by chloride ions (See section \u003cspan refid=\"Sec8\" class=\"InternalRef\"\u003e3.5\u003c/span\u003e). However, severe corrosion occurred after the addition of 0.2 molar Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions to the electrolyte. Also, the n values show a decreasing trend with the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e content of electrolyte. The n value is a sign of surface roughness \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. Surface attack by the Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions left behind a rough surface. The n value for an ideal capacitor is 1. The electric double layer on a rough surface shows a lower n value. After work hardening up to 30% strain the second relaxation time appeared could be due to intensive passive film formed on the nobler phases in the aforementioned galvanic couples like surface islands. The n values for samples with work hardening up to 30% strain are relatively lower than as-annealed samples due to the passive islands formation. Also, the charge transfer resistance is considerably larger than as-annealed samples. A notable increase in R\u003csub\u003ect\u003c/sub\u003e was observed in the 15% and 30% cold-compressed samples, suggesting that cold work promoted the formation of the protective layer, likely due to the increased surface higher energy. This protective layer, formed during the 24-hour immersion period, significantly improved corrosion resistance in these samples. The reduction in the PREN difference of the two phases could be considered as a reason for these observations.\u003c/p\u003e \u003cp\u003eIn contrast, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e(b), the corrosion behavior of LDX 2101 after 45% strain deviates from that of the other samples. In the sample with 45% strain, the surface arrangement was changed and full coverage of the steel surface occurred. With a considerable decrease in the PREN difference and disappearing galvanic effect, a relative barrier layer covers the entire surface of the metal. The large high-frequency phase angle values for the sample with 45% strain could be considered a sign of uniform barrier surface film formation \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. The largest charge transfer and the lowest double-layer CPE are recorded for the sample with 45% strain proving the best protective behavior among all samples. Generally, charge transfer resistance is directly correlated with corrosion resistance, where a larger Nyquist curve diameter corresponds to better corrosion resistance \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. The pitting corrosion reduction and impedance resistance improvement, due to the dislocation movement into the γ phases and consequent SIM formation, are the result of the corrosion study part which is explained in the next section with more details.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Corrosion Mechanism\u003c/h2\u003e \u003cp\u003eAccording to the characterization data and electrochemical analyses, the relationship between the microstructure and corrosion performance of LDX 2101, considering the presence or absence of chloride in the solution and the history of cold work, is schematically illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e. Several researchers have reported that the passive film developed on stainless steels typically consists of two distinct layers. The inner layer is composed of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, which serves as a p-type semiconductor, while the outer layer is composed of iron-rich oxide and hydroxide, functioning as an n-type semiconductor. The inner Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e layer plays a critical role in corrosion resistance by providing robust protection against corrosion, while the outer iron-rich layer contributes to the overall stability of the passive film \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan additionalcitationids=\"CR47 CR48\" citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn citric acid solution, corrosion at the γ/α interface and the α grain boundaries primarily occurs due to the higher energy of the phase boundary and the relatively lower resistance of the α phase, attributed to its lower EWF. With the addition of Cl\u003csup\u003eꟷ\u003c/sup\u003e to the acidic solution, pitting corrosion at phase boundaries and in the α phase becomes more pronounced, which is explained by its lower PREN. When cold strain is applied, dislocation movement is initiated, especially in the γ phase, due to cold plastic deformation, resulting in the formation of SIM in the γ phase. As the hardness of the γ phase significantly increases, deformation begins to occur in the α phase as well. The plastic deformation leads to the formation of SIM at the γ/α boundaries. Unlike γ and α phases, SIM regions are active and are more susceptible to corrosion \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. This increased activity, combined with SIM formation, accelerates corrosion in the γ regions, bringing their resistance closer to that of the less noble α phase, which acts as the cathode, thus slowing the rate of galvanic corrosion and consequent pitting. Furthermore, as the dislocation density increases, the surface energy of both phases rises, promoting the faster formation of a protective layer, which enhances corrosion resistance. In the meantime, the Cr\u003csub\u003e2\u003c/sub\u003eN precipitates are preferential areas for pit formation due to chromium depletion around them. These precipitates, typically located at grain boundaries, increase susceptibility to chloride-induced corrosion in these regions.\u003c/p\u003e \u003cp\u003eThe addition of chlorine to the citric acid solution increases the corrosiveness of the electrolyte, making ferrite phases, grain boundaries, and Cr\u003csub\u003e2\u003c/sub\u003eN regions more susceptible to pitting corrosion. Chlorine compromises the protective passive layer, reducing its effectiveness. In contrast, cold working enhances the formation of the passive layer, thereby hindering the initiation and growth of pits. Overall, based on surface roughness measurements of the immersion samples and electrochemical test results, chlorine exacerbates the corrosion of the ferrite phase, whereas cold working improves resistance to pitting corrosion.\u003c/p\u003e \u003cp\u003eA recent study by Assump\u0026ccedil;\u0026atilde;o et al. \u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e demonstrated that the corrosion properties of 2304 LDX were significantly enhanced through cold rolling, which induced residual compressive stresses and reduced nucleation sites for corrosion pits in chlorine-rich media. However, martensitic transformation adversely affects corrosion resistance by creating microstructural inhomogeneities, such as α'-martensite/austenite interfaces. In our case study, the decrease in austenite corrosion resistance due to SIM has narrowed the gap between the corrosion resistances of austenite and ferrite, thereby mitigating galvanic corrosion by reducing the anodic and cathodic potential difference.\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn the present research, the effects of cold work and chloride/citric acid concentration on the corrosion properties of LDX 2101 were investigated. For this purpose, CV, PDP, and EIS electrochemical tests were conducted, and phase evolutions after cold work, as well as corrosion damage, were analyzed using SEM, XRD, AFM, and OM. The most important results of this research are as follows:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eLDX 2101 consists of \u0026gamma; and \u0026alpha; phases, with Cr\u003csub\u003e2\u003c/sub\u003eN and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e precipitates also forming. Cr\u003csub\u003e2\u003c/sub\u003eN phases were observed along the \u0026alpha; grain boundaries and at the \u0026alpha;/\u0026gamma; interphase boundaries.\u003c/li\u003e\n \u003cli\u003eCold working in LDX 2101 initially deformed the \u0026gamma; phase, followed by the \u0026alpha; phase at higher strains. The formation of SIM in the \u0026gamma; phase and the increase in dislocation density in both phases resulted in a 54.7 % increase in hardness for the \u0026gamma; phase and an 11% increase for the \u0026alpha; phase after 45 % cold strain.\u003c/li\u003e\n \u003cli\u003eGalvanic corrosion in LDX 2101 was observed in citric acid, where the corrosion resistance of the \u0026alpha; phase was lower. With the addition of chloride to the solution, pitting corrosion occurred in the \u0026alpha; phase and at grain boundaries, with Cr\u003csub\u003e2\u003c/sub\u003eN precipitates serving as preferred corrosion sites. High concentrations of chloride and citric acid intensified the corrosion of LDX 2101.\u003c/li\u003e\n \u003cli\u003eAccording to the results of the immersion test and PDP data, cold work improved corrosion resistance in citric acid-chloride solutions. The faster formation of the protective layer in these samples, attributed to the increased density of dislocations and a more active surface, was the main reason for this improvement.\u003c/li\u003e\n \u003cli\u003eBased on the EIS data, after 24 h of immersion, the as-annealed sample exhibited the lowest corrosion resistance in the chloride-citric acid solution. Additionally, corrosion resistance improved at strains of 15 % and 30%, and in the 45 % deformed sample, the corrosion mechanism changed due to the formation of SIM and increased dislocation density, which resulted in enhanced passive film protection.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMazdak Izadi and Saeid Karimi conceived of the presented idea, developed the theory, verified the analytical methods, supervised the findings of this work. All authors discussed the results and contributed to the final manuscript.Mohammadreza Mokhtare performed the experiments, derived the models and analysed the data, and wrote the manuscript. All authors discussed the results and contributed to the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data generated and analyzed during this study are included in this article.\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003eIn the present research, the effects of cold work and chloride/citric acid concentration on the corrosion properties of LDX 2101 were investigated. For this purpose, CV, PDP, and EIS electrochemical tests were conducted, and phase evolutions after cold work, as well as corrosion damage, were analyzed using SEM, XRD, AFM, and OM. The most important results of this research are as follows:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eLDX 2101 consists of \u0026gamma; and \u0026alpha; phases, with Cr\u003csub\u003e2\u003c/sub\u003eN and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e precipitates also forming. Cr\u003csub\u003e2\u003c/sub\u003eN phases were observed along the \u0026alpha; grain boundaries and at the \u0026alpha;/\u0026gamma; interphase boundaries.\u003c/li\u003e\n \u003cli\u003eCold working in LDX 2101 initially deformed the \u0026gamma; phase, followed by the \u0026alpha; phase at higher strains. The formation of SIM in the \u0026gamma; phase and the increase in dislocation density in both phases resulted in a 54.7 % increase in hardness for the \u0026gamma; phase and an 11% increase for the \u0026alpha; phase after 45 % cold strain.\u003c/li\u003e\n \u003cli\u003eGalvanic corrosion in LDX 2101 was observed in citric acid, where the corrosion resistance of the \u0026alpha; phase was lower. With the addition of chloride to the solution, pitting corrosion occurred in the \u0026alpha; phase and at grain boundaries, with Cr\u003csub\u003e2\u003c/sub\u003eN precipitates serving as preferred corrosion sites. High concentrations of chloride and citric acid intensified the corrosion of LDX 2101.\u003c/li\u003e\n \u003cli\u003eAccording to the results of the immersion test and PDP data, cold work improved corrosion resistance in citric acid-chloride solutions. The faster formation of the protective layer in these samples, attributed to the increased density of dislocations and a more active surface, was the main reason for this improvement.\u003c/li\u003e\n \u003cli\u003eBased on the EIS data, after 24 h of immersion, the as-annealed sample exhibited the lowest corrosion resistance in the chloride-citric acid solution. Additionally, corrosion resistance improved at strains of 15 % and 30%, and in the 45 % deformed sample, the corrosion mechanism changed due to the formation of SIM and increased dislocation density, which resulted in enhanced passive film protection.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"LDX 2101, EIS, pitting corrosion, cold work, strain-induced martensite","lastPublishedDoi":"10.21203/rs.3.rs-6483885/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6483885/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e2101 Lean duplex stainless steel (LDX) is emerging as a strong competitor to traditional austenitic stainless steels in the food industry, thanks to its superior corrosion resistance and cost-effectiveness. This study investigates the impact of 15, 30 and 45% cold working and chlorine content on the corrosion behavior of LDX 2101 exposed to citric acid as the most common electrolyte in food industries. Detailed electrochemical and characterization techniques have been used in this study. The results reveal that 2101 LDX is composed of γ and α phases, with Cr\u003csub\u003e2\u003c/sub\u003eN and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e precipitates forming along grain and phase boundaries. Cold working primarily deforms the γ phase, leading to the formation of strain-induced martensite (SIM), and increases the hardness of α and γ phases. Galvanic and pitting corrosion was observed, especially in the α phase, where Cr\u003csub\u003e2\u003c/sub\u003eN precipitates act as pit initiation sites. While the presence of chloride ions accelerated corrosion rate, cold working enhanced the materials corrosion resistance by promoting the surface passive layer characteristics. Electrochemical impedance spectroscopy results indicated that the as-annealed sample showed the lowest corrosion resistance after 24 h of immersion. In contrast, samples subjected to 15% and 30% strain exhibited improved resistance with 23.5 and 46.7% reduction in i\u003csub\u003ecorr\u003c/sub\u003e, with a significant passive behavior observed in the 45% cold-worked sample.\u003c/p\u003e","manuscriptTitle":"The Combined Effect of Cold Work and Chloride Content on Corrosion Mechanism of 2101 Lean Duplex Stainless Steel in Citric Acid","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-05 06:32:50","doi":"10.21203/rs.3.rs-6483885/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f2b5e9e1-94f2-4cfc-a7bf-19990e4aa39d","owner":[],"postedDate":"May 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":47966660,"name":"Physical sciences/Chemistry"},{"id":47966661,"name":"Physical sciences/Engineering"},{"id":47966662,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-05-13T11:23:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-05 06:32:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6483885","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6483885","identity":"rs-6483885","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}