Superior Corrosion Inhibition Activity of CaO Nanoparticles Synthesized from Natural Sources toward Grade 202 Stainless-steel in Chloride-rich Media

Superior Corrosion Inhibition Activity of CaO Nanoparticles Synthesized from Natural Sources toward Grade 202 Stainless-steel in Chloride-rich Media | 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 Research Article Superior Corrosion Inhibition Activity of CaO Nanoparticles Synthesized from Natural Sources toward Grade 202 Stainless-steel in Chloride-rich Media M. H.N. REVON, NAMAL PRIYANTHA This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7479462/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 14 You are reading this latest preprint version Abstract Grade 202 Stainless Steel (SS Grade 202), an iron-based alloy with a reasonably high chromium content, is well-regarded for its notable resistance to corrosion in mild environments. Although SS Grade 202 is extensively employed in the industrial sector to develop corrosion-resistant material through further processing, effects of different chemical components present in the surrounding environment on its corrosion behavior in aggressive settings, and potential corrosion inhibitors under such conditions have not been thoroughly investigated. On the other hand, nanoparticles (NPs) inhibit corrosion by adsorption on metal surfaces thereby forming a protective barrier, thus preventing corrosive agents. NPs of CaO obtained from natural materials such as clamshells and limestone by calcination act as highly effective corrosion inhibitors due to their small size and large surface area promoting the passivation of oxide films. The ready availability of clamshells and limestone positions them as sustainable sources to produce CaO NPs, offering a cost-effective and environmentally responsible approach to corrosion protection. Corrosion rates determined with the aid of Tafel plots, depicted by CaO NPs from limestone at 0.05 M strength in the presence of 0.50 M HCl is 3.53×10 − 2 mmpy, which is much smaller when compared to CaO NPs synthesized by clamshells (1.24 mmpy). Corrosion rate mass loss Nyquist plots open circuit potential Tafel plots 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 Corrosion is a characteristic wonder that can harm metallic objects in dry or damp media causing significant financial misfortunes. The yearly budget ascribed to corrosion is estimated to be more than $ 500 billion within the United States alone [ 1 ]. Impressive endeavors are hence being conveyed to search for appropriate reagents as corrosion inhibitors of metallic objects. Successful corrosion inhibitors would associate with the interface of the target object, preventing its corrosion responses through passivating film arrangement, precipitation, or adsorption [ 2 ]. Corrosion restraint has been conveyed by the utilization of natural compounds and synthetic heterocyclic compounds [ 3 ]. Distinctive corrosion inhibitors are thus required depending on the type of corrosion system and its intended utilization, whether in typical situations or beneath aggressive conditions [ 4 ]. The corrosion rate of alloys, such as steel, can be moderated by inhibitors at low dosages which are as of now utilized in cooling frameworks, and oil and gas pipelines [ 5 ]. Moreover, considerable attention has been paid to corrosion inhibition in implementing coolant fluids for various fields [ 6 ]. Natural composite layer coatings have also been utilized to upgrade hindrance effectiveness [ 7 ]. Stainless steel (SS) majorly consists of Cr, and hence it shows corrosion resistance to some degree. It is broadly utilized underneath particular conditions in chemical and petrochemical forms managing with acidic, soluble, and salt arrangements [ 8 ]. Nevertheless, mild steel experiences corrosion in some media, such as aqueous H 3 PO 4 [ 9 , 10 ] unlike SS does. On the other hand, SS, broadly utilized in distinctive mechanical applications, is popular for its exceptional disintegration resistance, which is credited to the course of action of Cr-rich inactive films [ 11 ]. Other than being a Fe-based combination with Cr, SS moreover consists of Ni, N, and other components which lead to a high level of corrosion resistance [ 12 ]. Thus, a few grades of SS are made up of diverse compositions of alloying components to suit the conditions the combination must withstand [ 13 ]. Based on the environment that SS is exposed to, it tends to form a lean passive film that's rich in chromium oxide and/or hydrogen in this manner restraining corrosion [ 14 ]. There is a series of SS grades based on the percentage of Cr and Ni, and the 200 series have been well renowned for their high corrosion resistance together with cost-effectiveness. SS Grade 202 is the highly used alloy of Cr that is utilized in many industries including food/drug production, pharmaceutical industries, welding applications, automotive industries, cookware, and cutlery in addition to being used in open-air location outfitting [ 15 ]. In spite of the fact that Grade 202 Stainless Steel (SS Grade 202) is corrosion resistant, it is inclined to Galvanic, pitting, and crevice corrosions in some aggressive situations, such as chloride-rich environments, leading to harmful impact [ 16 ]. In order to protect SS Grade 202 from corrosion, suitable precautionary measures must be implemented. Corrosion inhibition which reduces the rate of attack on a material, such as a metal from a hostile environment, has been a major concern in avoiding corrosion impact on metals. As corrosion-inhibitive methods, various implementations have been deployed: Formation of passive films and using corrosion-inhibitive chemical constituents such as nitrate and phosphate-based inhibitors are some of them [ 17 ]. Due to natural reasons, it is essential to supplant the nitrite-based inhibitors with eco-friendly and less hurtful ones [ 18 ]. As an elective, phosphate-based inhibitors have been utilized as temporal inhibitors to diminish the disintegration and corrosion of metals and alloys [ 19 ]. Phosphate particles are able to advance ferrous phosphate precipitation on SS, and consequently, such inhibitors have picked up critical contemplations in different segments [ 20 ]. It has been shown that organic compounds, such as eugenol derivatives, have exhibited inhibition efficiency in the saline media, demonstrating the effectiveness of functional groups containing hetero atoms toward mitigating corrosion [ 21 ]. The direction of the present-day research on corrosion inhibition has focused on the use of nanoparticles, owing to their diminished molecular size and expanded number of dynamic centers within a given mass. This in the long term advances the successful physical/chemical adsorption of nanoscale inhibitors on the corroded metal surface. One application is to incorporate CuO into paints as a better passive coating for metallic bodies. Thus, the inspiration for the investigation of different compounds which have the same rock salt structure as CuO has been considered in this study. This study in this way executed to recognize the corrosion behavior of SS Grade 202 in different corrosive and salt exposures at diverse concentrations with uncommon emphasis on exploring the impact of CaO nanoparticles (NPs) as corrosion inhibitors. Obtaining high-purity CaO NPs from waste materials is a key component that has been considered in this study which would also contribute to a sustainable environment. Investigating which synthesizing method of CaO from waste material has the best corrosion-inhibitive impact on SS Grade 202 is emphasized in this study as the impact on NPs contributes to the corrosion inhibition mechanism of SS Grade 202. Thus, NPs synthesized from clamshell waste and limestone waste were separately examined within a broader concentration range of solution constituents. Moreover, centering on the introduction of SS to different concentrations of diverse CaO in the presence and absence of Cl ̄ environment was examined employing a multi-technique approach of mass loss measurements, electrochemical impedance spectroscopy (EIS) [ 22 ], Tafel slope analysis, and open circuit potential measurements (OCP) [ 23 ], to distinguish the impact Cl − interferent on restraint activity of CaO NPs toward corrosion stability of SS Grade 202. 2. Materials and Methods 2.1 Composition of SS 202 Circular specimens of SS Grade 202 (Table 1 ) were split into four pieces, each containing a quarter of the entire circle, after being cut to a height of 0.5 cm for mass loss and electrochemical measurements. X-ray fluorescence (XRF) spectrum recorded on Fischerscope Model-DF500FG-456 confirms the presence of Cr and Mn as major metallic alloy elements of SS Grade 202 (Fig. 1 ). All specimens were cleaned thoroughly with distilled water then by acetone and dried at room temperature. All experiments were performed under ambient conditions. Table 1 Composition of SS Grade 202 as a percentage (%) [ 24 ]. Stainless-Steel C Mn P Cu Si Cr Ni Fe N 202 ≤ 0.15 7.50–10.00 ≤ 0.06 ≤ 1.11 ≤ 1.00 17.0–19.0 4.0–6.0 ≤ 68.0 ≤ 0.25 2.2 Synthesis of CaO NPs CaO NPs synthesized from clamshells : Randomly selected waste clamshells were thoroughly washed with tap water, followed by deionized water to remove dust, impurities. Cleaned samples of clamshells were crushed to form small particles and mixed with a 1:9 ratio of conc. HCl and water until the clamshells were dissolved. Then 1.0 M NaOH solution was added, and the precipitate formed was undisturbed for 3.0 h and centrifuged at 4000 rpm for about 5.0 min. Thereafter, the resulting powder was washed with deionized water and kept for drying in an oven for about 2.0 h at 60 °C to remove moisture. Ultimately, the powder underwent calcination in a muffle furnace at a temperature of 1000°C for a duration of 1.0 h. [ 25 ]. CaO NPs synthesized from limestone Random sample of waste limestone was washed with tap water to remove dust, impurities. Cleaned samples of limestone were crushed to small sizes and calcinated in a muffle furnace at 1000 °C for 1.0 h [ 26 ]. The synthesized CaO nanoparticles were characterized utilizing XRF spectroscopy, X-ray diffraction (XRD) with a Rigaku Ultima IV theta-theta x-ray diffractometer (Japan), Fourier transform infrared (FTIR) spectroscopy through a Jasco FT/IR-6700, particle size analysis conducted with a Dual Scattering Particle Size Analyzer Nano DS, and scanning electron microscopy (SEM) using a Carl Zeiss evo ls 15. 2.3 Mass loss measurements For mass loss measurements, the initial mass of each SS specimen was recorded. Thereafter, specimens were immersed in test solutions, and taken out every 24 h, cleaned, dried, weighed, and immersed in the solution again [ 27 ]. Mass measurements were continued for one week. Mass loss was determined from the difference between pre-and post-immersion masses. The percentage mass loss was then determined using Eq. (1) [ 28 ]. All mass loss experiments were performed at ambient temperature. % Mass loss = \(\:\left[\frac{{m}_{i}-\:m}{{m}_{i}}\right]\) \(\:\:100\) (1) where m i and \(\:m\:\text{a}\text{r}\text{e}\:\text{t}\text{h}\) e masses of the specimen in the blank and test solutions, respectively. The impact of CaO NPs on mass loss was investigated in the HCl medium in the presence and absence of NaCl up to a range of concentrations to investigate the limiting concentration of CaO for strong corrosion inhibitory action for each extreme environment at ambient temperature. All mass loss measurements were triplicated. 2.4 Determination of electrochemical properties Electrochemical impedance spectroscopy (EIS) was performed using a PGSTAT-204 electrochemical analyzer using a three-electrode cell, within a frequency range between 1.0×10 6 Hz and 0.1 Hz [ 29 , 30 ]. The linear polarization technique was carried out to generate Tafel plots under the potential range from − 0.1 V to 0.1 V at a 10-mV s − 1 scan rate [ 31 ]. Open circuit potentials (OCP) of SS specimens were noted with respect to Ag(s)/AgCl(s)/KCl(aq) electrode to analyze the relationship between corrosion potential and its corrosion inhibition efficiency. 3. Results and Discussion 3.1 Characterization of CaO NPs synthesized from clamshells and limestone XRD analysis of CaO NPs The XRD pattern in Fig. 2 (a) clearly shows strong diffraction peaks at 2θ values of 32.27°, 37.43°, 53.97° and 64.30°, corresponding to the presence of cubic phase of CaO synthesized from clamshells (ASTM Card file No. 37-1497) [ 32 ]. Peaks at similar locations observed in Fig. 2 (b) also confirm the presence of CaO synthesized from limestone. FT‑IR investigation of CaO NPs The band at 3637 cm − 1 observed in the FTIR spectrum shown in Fig. 3 corresponds to O-H stretching, while the bands at 2986 cm − 1 , 1735 cm − 1 , 1359 cm − 1 , and 1219 cm − 1 can be associated with C-H stretching vibrations, as well as C = O stretching, C-O bending, and C-O stretching, respectively. The bands due to vibrations of C bonded to O would have arisen from CaCO 3 formed as a result of CO 2 absorption by CaO. More importantly, the characteristic band at 529 cm − 1 corresponds to the presence of CaO bond [ 33 ]. Similar characteristics peaks have been detected for both synthesized CaO from waste material clamshells and limestone. XRF investigation of CaO NPs XRF spectroscopic data conclude having 99.92% of CaO in synthesized NPs as the major constituent while 0.08% SrO was identified in the clamshells sample whilst CaO NPs obtained from limestone is found to have 99.49% CaO and the rest as SrO. 3.1.4 Particle size analysis of CaO NPs Dual scattering particle size analysis denotes that the mean value of CaO NPs synthesized from clamshells is 35.4 nm in diameter, while that synthesized from limestone is 4.3 nm, verifying that both varieties of particles fall within the nanometer scale. The distribution of particle diameter is broader with clamshells than with limestone. Compared to calcite in limestone, the aragonite structure in clamshells breaks down into CaO at a lower temperature. However, the uniformity of the thermal reaction is impacted by the presence of organic impurities, leading to the production of larger and more heterogeneous particles whilst, limestone is subjected to grinding or size-reduction processes, its predominantly calcite composition results in a uniform thermal breakdown to CaO, which produces finer and more homogeneous particles [ 34 ]. 3.1.5 SEM analysis of SS Grade 202 and CaO NPs The SEM images illustrate the surface characteristics of SS Grade 202 prior to and following exposure to HCl (Fig. 6 ), revealing that the initially smooth and intact surface transforms into a highly rough and porous texture post-exposure, characterized by considerable pitting and material loss, which signifies serious acid-induced corrosion and highlights the necessity for protective coatings or inhibitors. undefined The CaO formed from clamshells (Fig. 7 a) has a granular, irregular structure and comparatively uniform particle sizes. This implies that the biomaterial was successfully calcined, producing high-purity CaO. On the other hand, limestone-derived CaO is porous and has a higher surface area that may result in increased catalytic activity, making it ideal for environmental remediation and corrosion inhibition. Moreover, CaO from limestone (Fig. 7 b) shows a more compact, layered structure with fewer dispersed particles, indicating a denser and more crystalline material. Calcium oxide derived from limestone is perfect for applications requiring durability because of its smoother surface and higher degree of sintering or recrystallization during calcination, which suggest improved structural stability. The various morphologies demonstrate how the source material affects the final characteristics and possible applications of CaO. 3.2 Mass loss of SS Grade 202 in HCl acid solutions in the presence and absence of NaCl As expected, an increasing trend of mass loss of SS Grade 202 was observed when increasing the concentration of HCl acid solutions within the range from 0.10 M to 1.00 M (Fig. 8 ). Higher concentrations leading to higher mass losses emphasizing that Cl − ions perform as promoters of pitting corrosion of SS Grade 202, in addition to the corrosion promotion due to H 3 O + . It should also be noted that the SS specimen is completely dissolved after 2 days in 1.00 M HCl medium, whereas the specimen lost less than 20% of its mass even after 7 days in 0.10 M HCl medium showing the corrosion resistance of SS Grade 202 in mild acidic conditions. An increasing mass loss can be noticed at higher HCl concentrations [ 35 ]. Therefore, investigation of the corrosion behavior of SS Grade 202 in extreme environments such as HCl in the presence of NaCl is needed to improve corrosion stability in such aggressive environments. If SS Grade 202 could survive in an aggressive environment within a short period of time, it would be able to survive in mild conditions for a long period. Being a corrosion promoter, exposure of SS Grade 202 to an environment rich in Cl − ions, contributed by either HCl or NaCl, results in significant corrosion, as shown in Fig. 9 , which illustrates rapid increase in mass loss in the presence of different NaCl concentrations in 0.25 M HCl and 0.50 M HCl solutions. Long term exposure of SS Grade 202 for 7 days in mixed NaCl/HCl medium results in almost 100% mass loss in 1.00 M NaCl + 0.50 M HCl, whereas it drops little more than 50% in 1.00 M NaCl + 0.25 M HCl, indicating strong impact of both Cl − and H 3 O + toward corrosion. Stress corrosion cracking of stainless steel due to chloride, and the effect of temperature and pH have already been reported [ 36 ]. 3.3 Corrosion inhibition of SS Grade 202 with CaO NPs CaO forms a porous protective layer that acts as a corrosion inhibitor for SS Grade 202. The inhibition efficiency of SS Grade 202 is much higher due to nanoparticles of CaO. Superior corrosion inhibition ability of CaO NPs synthesized from both of clamshells and limestone is evident in Fig. 10 , which demonstrates the effect of the increase in the concentration of CaO NPs toward corrosion inhibition and that of HCl toward corrosion promotion. Between the two sources used to obtain CaO NPs, the corrosion inhibition is more significant with CaO NPs obtained from limestone that from clamshells although the difference is not signicant. Moreover, zero mass loss, i.e . excellent corrosion inhibition is observed in 0.25 M HCl with 0.10 M solution of CaO synthesized from clamshells while a solution of 0.025 M CaO synthesized from limestone provides similar inbitory action. The reactive corrosion inhibition species in this system is Ca 2+ ions which are formed when CaO is mixed with HCl solution. Because of their size and high surface energy, CaO particles at the nanoscale may possess special chemical characteristics. By stabilizing Ca 2+ ions in solution, these particles can improve surface interaction with SS Grade 202 and possibly accelerate the development of a corrosion-resistant protective layer.The dissolved Ca 2+ can contribute more successfully to the formation of a strong passive layer on Grade SS Grade 202 when the CaO particles are smaller. Because of its higher rate of dissolution and shorter ionic interaction distances, nano CaO may promote the formation of a more homogeneous and tightly bound passivation layer.Therefore, even if CaO dissolves in HCl to form Ca 2 ⁺ ions, the rate at which these ions are released and their ability to interact with the metal surface will determine how effective the corrosion inhibition of SS Grade 202. Concluding CaO synthesized from limestones illustrating superior corrosion inhibition [ 37 , 38 ]. Correlating the fact of physicochemical properties like larger surface area and tunable size lead to higher effectiveness of corrosion inhibition by forming a protective passive film through adsorption and barrier mechanism to avoid exposure of metal substrate from the aggressive environment [ 39 ]. 3.3 Corrosion Inhibition Determined by EIS Supporting the results as obtained in mass loss, CaO synthesized from both clamshells and limestone perform as superior corrosion inhibition at varing concentrations. The Nyquist plots illustrated in Fig. 11 demonstrate the electrochemical impedance characteristics of SS Grade 202 in HCl solutions containing CaO NPs produced from clamshells and limestone. The semicircle's diameter in each diagram signifies charge transfer resistance ( R ct ), which is directly associated with corrosion resistance. A larger semicircle signifies increased resistance and improved protection against corrosion. When comparing all diagrams, both sources of CaO improve corrosion resistance relative to the blank solution. CaO derived from clamshells displays an escalating protective effect with concentration, yet its potency seems to level off at elevated concentrations (Figire 11a and 11b). In contrast, in diagrams, limestone-derived CaO unvaryingly demonstrates greater semicircle diameters, especially at 0. 050 M, signifying a more stable and effective passivation effect. This implies that limestone-derived CaO creates a more consistent and protective barrier on the steel surface, lowering charge transfer and boosting corrosion resistance. The enhanced performance of limestone-derived CaO may be influenced by variations in purity, crystalline structure, or surface activity, which enhance adhesion and protective film formation. In summary, the assessment corroborates that limestone-derived CaO offers more efficient and lasting corrosion inhibition, establishing it as the preferred option for preventing stainless steel degradation in acidic settings. The phase angle component of the Bode plot of SS Grade 202 specimen in both HCl solution and CaO NP containing solutions show three turning points associated with three time-constants. These results lead to the presence of at least three resistor – capacitor (RC) pairs in the electrochemical equivalent circuit (EEC) in both systems. Figure 12 a depicting bode plots correspond to 0.25 M and 0.50 M HCl conclude having two turning points or two interphases. Two turning points, representing the formation of a weak passive film at high frequencies and the charge transfer process at the metal-solution interface at low frequencies, are observed in pure HCl solutions (Fig. 12 a), corresponding to two time constants. Accelerated corrosion is indicated by the impedance decreasing as the HCl concentration increases. On the other hand, a third turning point—which represents an intermediary process involving nanoparticle adsorption—is introduced by the addition of CaO nanoparticles (Fig. 12 b). The passive layer is improved, corrosion resistance is greatly increased, and charge transfer rates are decreased by the CaO nanoparticles. Elevated CaO NP concentrations (0.050 M and 0.100 M) demonstrate superior surface coverage and enhanced inhibition efficiency, as demonstrated by higher phase angles and elevated impedance values throughout the entire frequency spectrum. These findings demonstrate how well CaO nanoparticles work to reduce corrosion in acidic environments. EEC assest the impact of CaO passivation film of SS Grade 202 in the presence of HCl including resistances ( R ) and capacitors ( C ). Corresponding to phase angle diagrams, various interfaces can be merged to design respective EEC. The investigation of electrochemical impedance for SS Grade 202 in HCl was conducted using equivalent circuits to evaluate the influence of CaO nanoparticles on corrosion inhibition. In the absence of CaO, the system shows reduced polarization resistance, which suggests elevated corrosion rates. Conversely, the inclusion of CaO introduces an extra R-C element, symbolizing a protective layer that enhances the passivation of the surface. The heightened impedance values verify the efficiency of CaO in minimizing metal dissolution and enhancing corrosion resistance. The additional R-C element pair in Fig. 13 b corresponds the interface of metal-CaO passive film. Impact of R S and R P values on corrosion inhibitory action towards SS Grade 202 in the aggressive environment is apparent in Table 2 . The influence of CaO concentration and its origin on corrosion resistance is also apparent, with limestone-derived CaO offering marginally superior protection at elevated concentrations. Table 2 Polarizations resistance ( R P ) and solution resistance ( R s ) values for SS Grade 202 when immersed in different solutions, based on the electrochemical equivalent circuits. Solution R s / Ω R p1 / Ω R P2 / Ω R P3 / Ω C 1 / F C 2 / F C 3 / F HCl (0.50 M) 12.9 13.7 1.43 -- 2.02×10 − 9 2.47×10 − 6 -- Mixture of HCl (in 0.50 M) and CaO (in 0.05 M) by clamshells 6.33 633 1.68 3.75 1.57×10 − 12 2.49×10 − 6 1.54×10 − 6 Mixture of HCl (in 0.50 M) and CaO (in 0.10 M) by clamshells 7.22 723 2.75 5.65 900×10 − 15 698×10 − 9 973×10 − 6 Mixture of HCl (in 0.50 M) and CaO (in 0.025 M) by limestone 5.44 545 3.22 4.68 900×10 − 15 239×10 − 9 318×10 − 6 Mixture of HCl (in 0.50 M) and CaO (in 0.05 M) by limestone 6.48 649 2.92 4.94 900×10 − 15 423×10 − 9 398×10 − 6 Figure 14 exhibits corrosion inhibition of SS Grade 202 in the presence of CaO in aggressive environments, such as 0.50 M HCl. According to the inversely proportional relationship between corrosion potential and corrosion rate illustrates low corrosion potential feasible towards much higher corrosion inhibition efficiency. Increment of CaO concentrations illustrating superior corrosion inhibition by synthesizing both materials; clamshells and limestones. Figure 14 a depicts corrosion potential order of increased CaO from clamshells concentrations whilst much less corrosion potential from CaO same concentration synthesized from limestones. Comparison of corrosion inhibition from equal concentration of CaO NPs synthesized from both materials, CaO synthesized from limestone having lower corrosion potential can be considred as the better corrosion inhibitor synthesized source. Confronting the potential variation of CaO synthesized from both materials, the corrosion potentials are much higher from synthesized from limestone as in Fig. 14 b than that synthesized from clamshells. Moreover, electrochemical parameters determined from Tafel plots are given in Table 3 . Table 3 Tabulated values for corrosion potential ( E corr ), corrosion current density ( I corr ), and corrosion rate of SS Grade 202. Slopes of the anodic branch ( b a ) and the cathodoic branch ( b c ) have also been reported. Solution immersed E corr (V vs. Ag/AgCl/Cl − ) I corr (A cm − 2 ) |b a | (V/dec) |b c | (V/dec) Corrosion rate (mmpy) HCl (0.50 M) -0.329 6.92×10 − 4 1.58×10 − 1 8.75×10 − 2 4.02 Mixture of HCl (in 0.50 M) and CaO (in 0.05 M) by clamshell -0.296 2.14×10 − 4 2.52×10 − 1 7.35×10 − 1 1.24 Mixture of HCl (in 0.50 M) and CaO (in 0.10 M) by clamshell -0.252 1.00×10 − 4 1.55×10 − 1 0.179 5.8×10 − 1 Mixture of HCl (in 0.50 M) and CaO (in 0.025 M) by limestone -0.254 4.08×10 − 5 6.74×10 − 2 5.10×10 − 2 2.3×10 − 1 Mixture of HCl (in 0.50 M) and CaO (in 0.05 M) by limestone -0.252 6.09×10 − 6 6.84×10 − 2 6.61×10 − 2 3.53×10 − 2 3.5 OCP measurements. Apart from supporting facts for corrosion inhibition by CaO NPs from mass loss measurements, EIS measurements and Tafel slope measurements, OCP measurements illustrate prominent electrochemical properties based on varying corrosion potentials of metallic or alloy substrates. The OCP of a working electrode is an indication of the tendency of a metallic substrate to be subject to deterioration in a specific environment [ 40 ]. The metallic substrate can adopt toward the aggressive environment of the electrolyte by building a protective coating if the OCP continues to increase and remain stable at a fixed potential over time. Inversely proportional relationship between corrosion potential and corrosion rate can be visible illustrating higher corrosion at lower corrosion potentials. At both HCl concentrations in the absence of CaO NPs, low open circuit potentials can be observed which led to higher corrosion rate (Fig. 15 ). Having low corrosion potentials for HCl 0.50 M, when compared to 0.25 M HCl, confirms the corrosion promoting behavior of HCl towards SS 202. Further, CaO NPs synthesized from limestone demonstrates higher corrosion potentials having low corrosion rate than those synthesized from clamshells due to high surface area; being low nano scale particles. 4.0 Conclusion CaO synthesized from both limestone and clamshells depicts higher effectiveness corrosion inhibition towards SS Grade 202 in the presence of aggressive environment such as HCl. Additionally, Cl − acts as a corrosion enhancer for SS Grade 202, showing increased mass loss in environments with a high concentration of Cl − . Based on the mass loss technique, EIS, EEC, and Tafel graphs, CaO nanoparticles significantly contribute to improving the corrosion resistance of SS Grade 202. Limestone-derived CaO NPs consisting average particle size of 4.3 nm leading to higher surface area than that of in clamshells-derived CaO NPs. In exposure of 0.50 M HCl, in the presence of 0.05 M CaO synthesized from limestone illustrating 99.12% inhibition efficiency with a corrosion rate of 3.53×10 − 2 mmpy whilst, clamshells-derived CaO at same concentration having 69.15% inhibition efficiency with a corrosion rate of 1.24 mmpy. A straighten correlation of corrosion with H 3 O + depicting a feasible corrosion mechanism of CaO NPs. Both CaO derived by limestone and clamshells having much higher corrosion potentials than that of absence of CaO. Thus, study denotes not only the impact of CaO NPs derived from natural materials led to a sustainable corrosion inhibition outcome, but also utilize the modifications of existing polymer coatings as synergistic effect. Abbreviations NPs Nanoparticles EIS Electrochemical impedance spectroscopy IE Inhibition efficiency OCP Open circuit potentials R P Polarization resistance R S Solution resistance SS Stainless steel Declarations Conflicts of Interest The authors declare that there are no conflicts of interest. Consent for publication All authors have given the consent for the publication of the manuscript and the materials incorporated. Ethics approval Not applicable. This research did not involve any human or animal subjects. Author Contribution Author N. Priyantha contributed to the conceptualization of the study, funding acquisition, investigation and supervision. Data curation, data analysis, and writing the original draft of the manuscript were done by M.H.N. Revon. Both authors contributed to reviewing and editing of the manuscript. Acknowledgments Special appreciation for the immense support provided by the Department of Chemistry, Faculty of Science, University of Peradeniya, Sri Lanka. Data Availability The data that supports this study will be shared upon reasonable request to the corresponding author; Namal Priyantha. ( [email protected] ). References Afshari F, Ghomi ER, Dinari M, Ramakrishna S. Recent advances on the corrosion inhibition behavior of Schiff base compounds on mild steel in acidic media. Chem Select. 2023;8(9):24–30. https://doi.org/10.1002/slct.202203231 . Al-Amiery AA, Mohamad AB, Kadhum AAH, Shaker LM, Isahak WNRW, Takriff MS. Experimental and theoretical study on the corrosion inhibition of mild steel by nonanedioic acid derivative in hydrochloric acid solution. Sci Rep. 2022;12(1):4705–26. https://doi.org/10.1038/s41598-022-08146-8 . Alaoui LM, Kertit S, Bellaouchou A, Guenbour A, Benbachir A, Hammouti B. Phosphate of aluminum as corrosion inhibitor for steel in H 3 PO 4 . Portugaliae Electrochim Acta. 2007;26(4):339–47. https://doi.org/10.4152/pea.200804339 . Desai PD, Pawar CB, Avhad MS, More AP. Corrosion inhibitors for carbon steel: A review. Vietnam J Chem. 2022;61(1):15–42. https://doi.org/10.1002/vjch.202200111 . Konovalova V. (2021). The effect of temperature on the corrosion rate of iron-carbon alloys. Materials Today: Proceedings , 38(4), 1326–1329. https://doi.org/10.1016/j.matpr.2020.08.094 Verma C, Quraishi MA, Ebenso E, Hussain CM. Recent developments in sustainable corrosion inhibitors: Design, performance, and industrial scale applications. Mater Adv. 2021;2(12):3806–50. https://doi.org/10.1039/d0ma00681e . Nazari MH, Zhang Y, Mahmoodi A, Xu G, Yu J, Wu J, Shi X. Nanocomposite organic coatings for corrosion protection of metals: A review of recent advances. Prog Org Coat. 2022;162:106573–93. https://doi.org/10.1016/j.porgcoat.2021.106573 . Schino AD. Manufacturing and applications of Stainless Steels. Metals. 2020;10(3):327–40. 10.3390/met10030327 . Hong T, Nagumo M. The effect of chloride concentration on early stages of pitting for type 304 stainless steel revealed by the AC impedance method. Corros Sci. 1997;39(2):285–93. 10.1016/s0010-938x(96)00127-8 . Ramón J, Martínez I, Gandía-Romero J, Soto J. Improved Tafel-based potentiostatic approach for corrosion rate monitoring of reinforcing steel. J Nondestr Eval. 2022;41(4):70–95. https://doi.org/10.1007/s10921-022-00903-z . Karunanithi SP, Arasappan RK, Nallathambi SS. An overview on additive manufacturing of duplex stainless steels: Microstructure, mechanical properties, corrosion resistance, postheat treatment, and future perspectives. Steel Res Int. 2024;95(12):2400463–83. https://doi.org/10.1002/srin.202400463 . Heo J, Lee SY, Lee J, Alfantazi A, Cho SO. Improvement of corrosion resistance of stainless steel welded joint using a nanostructured oxide layer. Nanomaterials. 2021;11(4):838–51. https://doi.org/10.3390/nano11040838 . Khadom AA. Kinetics and synergistic effect of iodide ion and naphthylamine for the inhibition of corrosion reaction of mild steel in hydrochloric acid. Reaction Kinetics Mech Catal. 2015;115(2):463–81. 10.1007/s11144-015-0873-9 . Kim HJ, Hong JS, Choi JH, Han GS, Jung HS. Effect of phosphate ions on the formation of iron oxide/hydroxide as a stabilizer. J Solid State Chem. 2022;305:122688–122688. https://doi.org/10.1016/j.jssc.2021.122688 . Gu F, Zhang Y, Su Z, Tu Y, Liu S, Jiang T. Recovery of chromium from chromium-bearing slags produced in the stainless-steel smelting: A review. J Clean Prod. 2021;296:126467–88. https://doi.org/10.1016/j.jclepro.2021.126467 . Hong T, Nagumo M. The effect of chloride concentration on early stages of pitting for type 304 stainless steel revealed by the AC impedance method. Corros Sci. 1997;39(2):285–93. 10.1016/s0010-938x(96)00127-8 . Revon MHN, Priyantha N. Interference of Solution Constituents on Corrosion Inhibition of Phosphate Species on Grade 202 Stainless Steel. Discover Chem. 2024. https://doi.org/10.21203/rs.3.rs-5077929/v1 . Mandal S, Singh JK, Lee D-E, Park T. Effect of phosphate-based inhibitor on corrosion kinetics and mechanism for formation of passive film onto the steel rebar in chloride-containing pore solution. Materials. 2020;13(16):3642–66. 10.3390/ma13163642 . Zhang J, Lu X, Zhang J, Zhang L, Zhu C, Zhang Y, Wu T. Corrosion-inhibition effect of different phosphate compounds for carbon steel in chloride-contaminated mortars. Int J Electrochem Sci. 2019;14(9):8601–10. https://doi.org/10.20964/2019.09.29 . Kim HJ, Hong JS, Choi JH, Han GS, Jung HS. Effect of phosphate ions on the formation of iron oxide/hydroxide as a stabilizer. J Solid State Chem. 2022;305:122688–122688. https://doi.org/10.1016/j.jssc.2021.122688 . Priyantha N, Jayasingha JMS, Wijesooriya WMGS. Inhibitive action of selected model compounds of eugenol on mild steel corrosion in salty medium. Prot Met Phys Chem Surf. 2021;57(2):412–21. https://doi.org/10.1134/s2070205121010159 . Priyantha N, Jayaweera P, Macdonald DD, Sun A. An electrochemical impedance study of Alloy 22 in NaCl brine at elevated temperature. I. Corrosion behavior. J Electroanal Chem. 2004;572(2):409–19. https://doi.org/10.1016/j.jelechem.2004.06.031 . Macdonald DD, Priyantha N, Jayaweera P, Engelhardt G, Davydov A. The localized corrosion of Alloy 22 in simulated HLNW environments. Corrosion. 2004;61(9):857–71. https://doi.org/10.5006/1.3280655 . 202 Stainless Steel: Composition, Properties, Applications, Processes, and More - SteelPRO Group. (2024, October 6). SteelPro. https://steelprogroup.com/stainless-steel/grades/grade-202/ Kumar S, Singh S, Narasimhappa P, Varshney R, Singh J, Khan NA, Zahmatkesh S, Ramamurthy PC, Shehata N, Kiran GN, Sunil K. Green and sustainable synthesis of CaO nanoparticles: Its solicitation as a sensor material and electrochemical detection of urea. Sci Rep. 2023;13(1):19995–20007. https://doi.org/10.1038/s41598-023-46728-2\ . Suprapto S, Fauziah TR, Sangi MS, Oetami TP, Qoniah I, Prasetyoko D. Calcium oxide from limestone as solid base catalyst in transesterification of reutealis trisperma oil. Indonesian J Chem. 2018;16(2):208–13. https://doi.org/10.22146/ijc.21165 . Alaoui LM, Kertit S, Bellaouchou A, Guenbour A, Benbachir A, Hammouti B. Phosphate of aluminum as corrosion inhibitor for steel in H 3 PO 4 . Portugaliae Electrochim Acta. 2007;26(4):339–47. https://doi.org/10.4152/pea.200804339 . Shwetha KM, Praveen PBM, Devendra BK. A review on corrosion inhibitors: types, mechanisms, electrochemical analysis, corrosion rate and efficiency of corrosion inhibitors on mild steel in an acidic environment. Results Surf Interfaces. 2024;16:100258–73. https://doi.org/10.1016/j.rsurfi.2024.100258 . Benabdellah M, Benkaddour M, Hammouti B, Bendahhou B, Aouniti A. Inhibition of steel corrosion in 2 M H 3 PO 4 by artemisia oil. Appl Surf Sci. 2006;252(18):6212–7. https://doi.org/10.1016/j.apsusc.2005.08.030 . Birla MS, Gabriel BI, Venkatraman MS, Cole IS, Moorthy GC, Emmanuel B. (2022). Theory of impedance for initial corrosion of metals under a thin electrolyte layer: a coupled charge transfer-diffusion model. Journal of Chemical Sciences/Proceedings of the Indian Academy of Sciences. Chemical sciences , 134(1), 4–10. https://doi.org/10.1007/s12039-021-02025-x Ramón J, Martínez I, Gandía-Romero J, Soto J. Improved Tafel-based potentiostatic approach for corrosion rate monitoring of reinforcing steel. J Nondestr Eval. 2022;41(4):70–95. https://doi.org/10.1007/s10921-022-00903-z . Scialla S, Carella F, Dapporto M, Sprio S, Piancastelli A, Palazzo B, Adamiano A, Degli Esposti L, Iafisco M, Piccirillo C. Mussel shell-derived macroporous 3D scaffold: Characterization and optimization study of a bioceramic from the circular economy. Mar Drugs. 2020;18(6):309–24. https://doi.org/10.3390/md18060309 . Vijai KA, Reshma M, Kannan M, Muthamil Selvan S, Chaturvedi S, Shalan AE, Govindaraju K. Preparation and characterization of calcium oxide nanoparticles from marine molluscan shell waste as nutrient source for plant growth. J Nanostructure Chem. 2021;11(2):161–71. https://doi.org/10.1007/s40097-020-00376-4 . Khalil, Rusli RK, and Andri. the effects of calcination on mineral composition and physical properties of limestones and oyster shells derived from different sources. World’s Veterinary J. 2021;11(4):578–86. https://doi.org/10.54203/scil.2021.wvj73 . Pardo A, Otero E, Merino MC, López MD, Utrilla MV, Moreno F. Influence of pH and chloride concentration on the pitting and crevice corrosion behavior of high-alloy stainless steels. Corrosion. 2000;56(4):411–8. https://doi.org/10.5006/1.3280545 . Scharfstein LR, Brindley WF. Chloride stress corrosion cracking of austenitic stainless steel—effect of temperature and pH. Corrosion. 1958;14(12):60–4. https://doi.org/10.5006/0010-9312-14.12.60 . Shao HB, Wang JM, Zhang Z, Zhang JQ, Cao CN. The cooperative effect of calcium ions and tartrate ions on the corrosion inhibition of pure aluminum in an alkaline solution. Mater Chem Phys. 2002;77(2):305–9. https://doi.org/10.1016/s0254-0584(02)00006-8 . Nam ND, Bian MZ, Forsyth M, Seter M, Tan M, Shin KS. Effect of calcium oxide on the corrosion behaviour of AZ91 magnesium alloy. Corros Sci. 2012;64:263–71. https://doi.org/10.1016/j.corsci.2012.07.026 . Alao AO, Popoola AP, Sanni O. The influence of nanoparticle inhibitors on the corrosion protection of some industrial metals: A Review. J Bio- Tribo-Corrosion. 2022b;8(3):68–83. https://doi.org/10.1007/s40735-022-00665-1 . Senthooran R, Revon MHN, Priyantha N. Cinnamon leaf extract as an effective inhibitor for mild steel corrosion in pickling bath environments. Discover Chem. 2025;2(1):18–33. https://doi.org/10.1007/s44371-025-00083-5 . Additional Declarations No competing interests reported. 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1","display":"","copyAsset":false,"role":"figure","size":14499,"visible":true,"origin":"","legend":"\u003cp\u003eXRF spectrum of SS Grade 202 specimen.\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/19e3e221f729f03c2cdce952.jpg"},{"id":93527975,"identity":"61eaeea5-8e25-4e3b-8cbd-89588b390d27","added_by":"auto","created_at":"2025-10-14 20:18:25","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":55803,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns CaO NPs (a) synthesized from clamshells (b) synthesized from limestone\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/98a44fd9f66eefba0d41258e.jpg"},{"id":93528618,"identity":"858d9b38-51e5-4413-85a5-af69d1efe089","added_by":"auto","created_at":"2025-10-14 20:26:25","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":47298,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of CaO NPs (a) pure substance (b) synthesized from clamshells (c) synthesized from limestone.\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/488827dfbf13098aa83565a8.jpg"},{"id":93527541,"identity":"12392888-8152-481c-b7ec-46adf3d0e32a","added_by":"auto","created_at":"2025-10-14 20:10:26","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":79962,"visible":true,"origin":"","legend":"\u003cp\u003eXRF spectrum of synthesized CaO NPs from (a) clamshells (b) limestones.\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/e98183e036a0122d6ff373ce.jpg"},{"id":93527533,"identity":"839e71e8-df80-41c3-bce5-ffcf7cdb03c6","added_by":"auto","created_at":"2025-10-14 20:10:25","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":72067,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution of CaO NPs synthesized from clamshells and limestone.\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/f5859f4f5f1b4a366b2e454c.jpg"},{"id":93527539,"identity":"00defe33-ff62-4ec5-85fe-2635fbd4b8f4","added_by":"auto","created_at":"2025-10-14 20:10:26","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":249301,"visible":true,"origin":"","legend":"\u003cp\u003eSEM analysis images of SS Grade 202 in the (a) absence and (b) presence of HCl 0.50 M.\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/fb46c326c7d05400b3cb239b.jpg"},{"id":93527984,"identity":"65cd9a77-6485-4ddf-98cd-4d6c77e39269","added_by":"auto","created_at":"2025-10-14 20:18:26","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":207155,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of CaO synthesized from (a) clamshells and (b) limestone.\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/de1c7959a5d08033569c21c9.jpg"},{"id":93528623,"identity":"09361d32-a228-4798-a921-37fdded20ba4","added_by":"auto","created_at":"2025-10-14 20:26:26","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":61483,"visible":true,"origin":"","legend":"\u003cp\u003eMass loss percentage of SS Grade 202 in HCl solutions of different concentrations.\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/5b6d4143d816177d27424539.jpg"},{"id":93527979,"identity":"ce3a58a5-a769-4902-aa41-9a4d5f8c7308","added_by":"auto","created_at":"2025-10-14 20:18:26","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":59712,"visible":true,"origin":"","legend":"\u003cp\u003eMass loss percentage of SS Grade 202 in different NaCl in the presence of (a) 0.25 M HCl and (b) 0.50 M HCl.\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/b478e7dd31f5e3a8a05f10c3.jpg"},{"id":93527593,"identity":"ecd7cc38-ed7b-4579-9b65-184540f8467e","added_by":"auto","created_at":"2025-10-14 20:10:27","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":109156,"visible":true,"origin":"","legend":"\u003cp\u003eMass loss of SS Grade 202 in HCl solutions after addition of CaO NPs at different concentrations; CaO synthesized from clamshells in (a) 0.25 M HCl (b) 0.50 M HCl; and CaO synthesized from limestone in (c) 0.25 M HCl and (d) 0.50 M HCl.\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/a3998d566628ef90fc197b2d.jpg"},{"id":93527980,"identity":"b4f62a9c-df91-4651-b132-3a386c6b9136","added_by":"auto","created_at":"2025-10-14 20:18:26","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":109318,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plots of 202 SS in HCl solutions after addition of CaO NP at different concentrations; CaO synthesized from clamshells in (a) 0.25 M HCl (b) 0.50 M HCl; and CaO synthesized from limestone in (c) 0.25 M HCl and (d) 0.50 M HCl.\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/a40765d310785a8d07ee025e.jpg"},{"id":93527986,"identity":"6a52feb5-1165-41a1-ad87-34ea2228b6d9","added_by":"auto","created_at":"2025-10-14 20:18:26","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":116975,"visible":true,"origin":"","legend":"\u003cp\u003eBode plots of Grade 202 SS in HCl solutions (a) 0.25 M HCl and 0.50 M; (b) after addition of CaO NPs at different concentrations in 0.25 M HCl.\u003c/p\u003e","description":"","filename":"Picture12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/4ec0b181e7e5ab2530b30cad.jpg"},{"id":93528622,"identity":"0bd9e916-c15f-4930-b360-e22483b849e6","added_by":"auto","created_at":"2025-10-14 20:26:26","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":45645,"visible":true,"origin":"","legend":"\u003cp\u003eEEC for HCl in (a) absence and (b) presence of CaO.\u003c/p\u003e","description":"","filename":"Picture13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/e4bff1a645cb23ea453e48dc.jpg"},{"id":93527556,"identity":"588df16c-365d-4431-80fe-67147bacbe02","added_by":"auto","created_at":"2025-10-14 20:10:26","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":86743,"visible":true,"origin":"","legend":"\u003cp\u003eTafel plots of Grade 202 SS in HCl solutions 0.50 M HCl in presence and absence of CaO NPs at different concentrations synthesized from (a) clamshells and (b) limestone.\u003c/p\u003e","description":"","filename":"Picture14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/3759e8c67ea55c9f28ea6d3b.jpg"},{"id":93527537,"identity":"d1a15882-3327-48da-bd8d-4a006d901cc0","added_by":"auto","created_at":"2025-10-14 20:10:25","extension":"jpg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":81297,"visible":true,"origin":"","legend":"\u003cp\u003eOCP values of SS Grade 202 in (a) 0.25 M (b) 0.50 M HCl in the presence and absence of CaO NPs synthesized from clamshells and limestones.\u003c/p\u003e","description":"","filename":"Picture15.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/02db4362d80f3744c953892f.jpg"},{"id":93528715,"identity":"71e7cb25-d9fd-4cfd-9caa-02725139753e","added_by":"auto","created_at":"2025-10-14 20:34:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2328502,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/e9eadd8c-0abc-4e64-975f-04655331b535.pdf"},{"id":93527976,"identity":"1aae3298-3ec7-434a-a9e8-ba55b82738f3","added_by":"auto","created_at":"2025-10-14 20:18:25","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":13753,"visible":true,"origin":"","legend":"","description":"","filename":"Highlights.docx","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/c74644358cb4a05e4ec4a5c0.docx"},{"id":93527532,"identity":"0c1b9a16-1b1b-439b-b276-8f85f0107acb","added_by":"auto","created_at":"2025-10-14 20:10:25","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1520046,"visible":true,"origin":"","legend":"","description":"","filename":"GACaOMS.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7479462/v1/190c1ba42105d98cb106dd80.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Superior Corrosion Inhibition Activity of CaO Nanoparticles Synthesized from Natural Sources toward Grade 202 Stainless-steel in Chloride-rich Media","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCorrosion is a characteristic wonder that can harm metallic objects in dry or damp media causing significant financial misfortunes. The yearly budget ascribed to corrosion is estimated to be more than \u003cspan\u003e$\u003c/span\u003e500\u0026nbsp;billion within the United States alone [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Impressive endeavors are hence being conveyed to search for appropriate reagents as corrosion inhibitors of metallic objects. Successful corrosion inhibitors would associate with the interface of the target object, preventing its corrosion responses through passivating film arrangement, precipitation, or adsorption [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Corrosion restraint has been conveyed by the utilization of natural compounds and synthetic heterocyclic compounds [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Distinctive corrosion inhibitors are thus required depending on the type of corrosion system and its intended utilization, whether in typical situations or beneath aggressive conditions [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The corrosion rate of alloys, such as steel, can be moderated by inhibitors at low dosages which are as of now utilized in cooling frameworks, and oil and gas pipelines [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Moreover, considerable attention has been paid to corrosion inhibition in implementing coolant fluids for various fields [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Natural composite layer coatings have also been utilized to upgrade hindrance effectiveness [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eStainless steel (SS) majorly consists of Cr, and hence it shows corrosion resistance to some degree. It is broadly utilized underneath particular conditions in chemical and petrochemical forms managing with acidic, soluble, and salt arrangements [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Nevertheless, mild steel experiences corrosion in some media, such as aqueous H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] unlike SS does. On the other hand, SS, broadly utilized in distinctive mechanical applications, is popular for its exceptional disintegration resistance, which is credited to the course of action of Cr-rich inactive films [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Other than being a Fe-based combination with Cr, SS moreover consists of Ni, N, and other components which lead to a high level of corrosion resistance [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Thus, a few grades of SS are made up of diverse compositions of alloying components to suit the conditions the combination must withstand [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Based on the environment that SS is exposed to, it tends to form a lean passive film that's rich in chromium oxide and/or hydrogen in this manner restraining corrosion [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThere is a series of SS grades based on the percentage of Cr and Ni, and the 200 series have been well renowned for their high corrosion resistance together with cost-effectiveness. SS Grade 202 is the highly used alloy of Cr that is utilized in many industries including food/drug production, pharmaceutical industries, welding applications, automotive industries, cookware, and cutlery in addition to being used in open-air location outfitting [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In spite of the fact that Grade 202 Stainless Steel (SS Grade 202) is corrosion resistant, it is inclined to Galvanic, pitting, and crevice corrosions in some aggressive situations, such as chloride-rich environments, leading to harmful impact [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In order to protect SS Grade 202 from corrosion, suitable precautionary measures must be implemented. Corrosion inhibition which reduces the rate of attack on a material, such as a metal from a hostile environment, has been a major concern in avoiding corrosion impact on metals. As corrosion-inhibitive methods, various implementations have been deployed: Formation of passive films and using corrosion-inhibitive chemical constituents such as nitrate and phosphate-based inhibitors are some of them [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Due to natural reasons, it is essential to supplant the nitrite-based inhibitors with eco-friendly and less hurtful ones [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. As an elective, phosphate-based inhibitors have been utilized as temporal inhibitors to diminish the disintegration and corrosion of metals and alloys [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Phosphate particles are able to advance ferrous phosphate precipitation on SS, and consequently, such inhibitors have picked up critical contemplations in different segments [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. It has been shown that organic compounds, such as eugenol derivatives, have exhibited inhibition efficiency in the saline media, demonstrating the effectiveness of functional groups containing hetero atoms toward mitigating corrosion [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe direction of the present-day research on corrosion inhibition has focused on the use of nanoparticles, owing to their diminished molecular size and expanded number of dynamic centers within a given mass. This in the long term advances the successful physical/chemical adsorption of nanoscale inhibitors on the corroded metal surface. One application is to incorporate CuO into paints as a better passive coating for metallic bodies. Thus, the inspiration for the investigation of different compounds which have the same rock salt structure as CuO has been considered in this study. This study in this way executed to recognize the corrosion behavior of SS Grade 202 in different corrosive and salt exposures at diverse concentrations with uncommon emphasis on exploring the impact of CaO nanoparticles (NPs) as corrosion inhibitors.\u003c/p\u003e\u003cp\u003eObtaining high-purity CaO NPs from waste materials is a key component that has been considered in this study which would also contribute to a sustainable environment. Investigating which synthesizing method of CaO from waste material has the best corrosion-inhibitive impact on SS Grade 202 is emphasized in this study as the impact on NPs contributes to the corrosion inhibition mechanism of SS Grade 202. Thus, NPs synthesized from clamshell waste and limestone waste were separately examined within a broader concentration range of solution constituents. Moreover, centering on the introduction of SS to different concentrations of diverse CaO in the presence and absence of Cl ̄ environment was examined employing a multi-technique approach of mass loss measurements, electrochemical impedance spectroscopy (EIS) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], Tafel slope analysis, and open circuit potential measurements (OCP) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], to distinguish the impact Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e interferent on restraint activity of CaO NPs toward corrosion stability of SS Grade 202.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Composition of SS 202\u003c/h2\u003e\u003cp\u003eCircular specimens of SS Grade 202 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) were split into four pieces, each containing a quarter of the entire circle, after being cut to a height of 0.5 cm for mass loss and electrochemical measurements. X-ray fluorescence (XRF) spectrum recorded on Fischerscope Model-DF500FG-456 confirms the presence of Cr and Mn as major metallic alloy elements of SS Grade 202 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). All specimens were cleaned thoroughly with distilled water then by acetone and dried at room temperature. All experiments were performed under ambient conditions.\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\u003eComposition of SS Grade 202 as a percentage (%) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\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\u003eStainless-Steel\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMn\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCu\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSi\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\u003eNi\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eFe\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e202\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.50\u0026ndash;10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e17.0\u0026ndash;19.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e4.0\u0026ndash;6.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;68.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;0.25\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\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Synthesis of CaO NPs\u003c/h2\u003e\u003cp\u003e\u003cem\u003eCaO NPs synthesized from clamshells\u003c/em\u003e: Randomly selected waste clamshells were thoroughly washed with tap water, followed by deionized water to remove dust, impurities. Cleaned samples of clamshells were crushed to form small particles and mixed with a 1:9 ratio of conc. HCl and water until the clamshells were dissolved. Then 1.0 M NaOH solution was added, and the precipitate formed was undisturbed for 3.0 h and centrifuged at 4000 rpm for about 5.0 min. Thereafter, the resulting powder was washed with deionized water and kept for drying in an oven for about 2.0 h at 60 \u0026deg;C to remove moisture. Ultimately, the powder underwent calcination in a muffle furnace at a temperature of 1000\u0026deg;C for a duration of 1.0 h. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCaO NPs synthesized from limestone\u003c/strong\u003e\u003cp\u003eRandom sample of waste limestone was washed with tap water to remove dust, impurities. Cleaned samples of limestone were crushed to small sizes and calcinated in a muffle furnace at 1000 \u0026deg;C for 1.0 h [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003c/p\u003e\u003cp\u003eThe synthesized CaO nanoparticles were characterized utilizing XRF spectroscopy, X-ray diffraction (XRD) with a Rigaku Ultima IV theta-theta x-ray diffractometer (Japan), Fourier transform infrared (FTIR) spectroscopy through a Jasco FT/IR-6700, particle size analysis conducted with a Dual Scattering Particle Size Analyzer Nano DS, and scanning electron microscopy (SEM) using a Carl Zeiss evo ls 15.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Mass loss measurements\u003c/h2\u003e\u003cp\u003eFor mass loss measurements, the initial mass of each SS specimen was recorded. Thereafter, specimens were immersed in test solutions, and taken out every 24 h, cleaned, dried, weighed, and immersed in the solution again [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Mass measurements were continued for one week. Mass loss was determined from the difference between pre-and post-immersion masses. The percentage mass loss was then determined using Eq.\u0026nbsp;(1) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. All mass loss experiments were performed at ambient temperature.\u003c/p\u003e\u003cp\u003e% Mass loss = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left[\\frac{{m}_{i}-\\:m}{{m}_{i}}\\right]\\)\u003c/span\u003e\u003c/span\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\:100\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003em\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:m\\:\\text{a}\\text{r}\\text{e}\\:\\text{t}\\text{h}\\)\u003c/span\u003e\u003c/span\u003ee masses of the specimen in the blank and test solutions, respectively. The impact of CaO NPs on mass loss was investigated in the HCl medium in the presence and absence of NaCl up to a range of concentrations to investigate the limiting concentration of CaO for strong corrosion inhibitory action for each extreme environment at ambient temperature. All mass loss measurements were triplicated.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Determination of electrochemical properties\u003c/h2\u003e\u003cp\u003eElectrochemical impedance spectroscopy (EIS) was performed using a PGSTAT-204 electrochemical analyzer using a three-electrode cell, within a frequency range between 1.0\u0026times;10\u003csup\u003e6\u003c/sup\u003e Hz and 0.1 Hz [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The linear polarization technique was carried out to generate Tafel plots under the potential range from \u0026minus;\u0026thinsp;0.1 V to 0.1 V at a 10-mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e scan rate [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Open circuit potentials (OCP) of SS specimens were noted with respect to Ag(s)/AgCl(s)/KCl(aq) electrode to analyze the relationship between corrosion potential and its corrosion inhibition efficiency.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Characterization of CaO NPs synthesized from clamshells and limestone\u003c/h2\u003e\u003cp\u003e\u003cem\u003eXRD analysis of CaO NPs\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe XRD pattern in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a) clearly shows strong diffraction peaks at 2θ values of 32.27\u0026deg;, 37.43\u0026deg;, 53.97\u0026deg; and 64.30\u0026deg;, corresponding to the presence of cubic phase of CaO synthesized from clamshells (ASTM Card file No. 37-1497) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Peaks at similar locations observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b) also confirm the presence of CaO synthesized from limestone.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eFT‑IR investigation of CaO NPs\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe band at 3637 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e observed in the FTIR spectrum shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e corresponds to O-H stretching, while the bands at 2986 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1735 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1359 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1219 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e can be associated with C-H stretching vibrations, as well as C\u0026thinsp;=\u0026thinsp;O stretching, C-O bending, and C-O stretching, respectively. The bands due to vibrations of C bonded to O would have arisen from CaCO\u003csub\u003e3\u003c/sub\u003e formed as a result of CO\u003csub\u003e2\u003c/sub\u003e absorption by CaO. More importantly, the characteristic band at 529 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the presence of CaO bond [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Similar characteristics peaks have been detected for both synthesized CaO from waste material clamshells and limestone.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eXRF investigation of CaO NPs\u003c/em\u003e\u003c/p\u003e\u003cp\u003eXRF spectroscopic data conclude having 99.92% of CaO in synthesized NPs as the major constituent while 0.08% SrO was identified in the clamshells sample whilst CaO NPs obtained from limestone is found to have 99.49% CaO and the rest as SrO.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e3.1.4 Particle size analysis of CaO NPs\u003c/h2\u003e\u003cp\u003eDual scattering particle size analysis denotes that the mean value of CaO NPs synthesized from clamshells is 35.4 nm in diameter, while that synthesized from limestone is 4.3 nm, verifying that both varieties of particles fall within the nanometer scale. The distribution of particle diameter is broader with clamshells than with limestone. Compared to calcite in limestone, the aragonite structure in clamshells breaks down into CaO at a lower temperature. However, the uniformity of the thermal reaction is impacted by the presence of organic impurities, leading to the production of larger and more heterogeneous particles whilst, limestone is subjected to grinding or size-reduction processes, its predominantly calcite composition results in a uniform thermal breakdown to CaO, which produces finer and more homogeneous particles [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.1.5 SEM analysis of SS Grade 202 and CaO NPs\u003c/h2\u003e\u003cp\u003eThe SEM images illustrate the surface characteristics of SS Grade 202 prior to and following exposure to HCl (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), revealing that the initially smooth and intact surface transforms into a highly rough and porous texture post-exposure, characterized by considerable pitting and material loss, which signifies serious acid-induced corrosion and highlights the necessity for protective coatings or inhibitors.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\n\u003ch3\u003eundefined\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe CaO formed from clamshells (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) has a granular, irregular structure and comparatively uniform particle sizes. This implies that the biomaterial was successfully calcined, producing high-purity CaO. On the other hand, limestone-derived CaO is porous and has a higher surface area that may result in increased catalytic activity, making it ideal for environmental remediation and corrosion inhibition. Moreover, CaO from limestone (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb) shows a more compact, layered structure with fewer dispersed particles, indicating a denser and more crystalline material. Calcium oxide derived from limestone is perfect for applications requiring durability because of its smoother surface and higher degree of sintering or recrystallization during calcination, which suggest improved structural stability. The various morphologies demonstrate how the source material affects the final characteristics and possible applications of CaO.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003e\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e3.2 Mass loss of SS Grade 202 in HCl acid solutions in the presence and absence of NaCl\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs expected, an increasing trend of mass loss of SS Grade 202 was observed when increasing the concentration of HCl acid solutions within the range from 0.10 M to 1.00 M (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Higher concentrations leading to higher mass losses emphasizing that Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions perform as promoters of pitting corrosion of SS Grade 202, in addition to the corrosion promotion due to H\u003csub\u003e3\u003c/sub\u003eO\u003csup\u003e+\u003c/sup\u003e. It should also be noted that the SS specimen is completely dissolved after 2 days in 1.00 M HCl medium, whereas the specimen lost less than 20% of its mass even after 7 days in 0.10 M HCl medium showing the corrosion resistance of SS Grade 202 in mild acidic conditions. An increasing mass loss can be noticed at higher HCl concentrations [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTherefore, investigation of the corrosion behavior of SS Grade 202 in extreme environments such as HCl in the presence of NaCl is needed to improve corrosion stability in such aggressive environments. If SS Grade 202 could survive in an aggressive environment within a short period of time, it would be able to survive in mild conditions for a long period. Being a corrosion promoter, exposure of SS Grade 202 to an environment rich in Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e ions, contributed by either HCl or NaCl, results in significant corrosion, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, which illustrates rapid increase in mass loss in the presence of different NaCl concentrations in 0.25 M HCl and 0.50 M HCl solutions. Long term exposure of SS Grade 202 for 7 days in mixed NaCl/HCl medium results in almost 100% mass loss in 1.00 M NaCl\u0026thinsp;+\u0026thinsp;0.50 M HCl, whereas it drops little more than 50% in 1.00 M NaCl\u0026thinsp;+\u0026thinsp;0.25 M HCl, indicating strong impact of both Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e and H\u003csub\u003e3\u003c/sub\u003eO\u003csup\u003e+\u003c/sup\u003e toward corrosion. Stress corrosion cracking of stainless steel due to chloride, and the effect of temperature and pH have already been reported [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Corrosion inhibition of SS Grade 202 with CaO NPs\u003c/h2\u003e\u003cp\u003eCaO forms a porous protective layer that acts as a corrosion inhibitor for SS Grade 202. The inhibition efficiency of SS Grade 202 is much higher due to nanoparticles of CaO. Superior corrosion inhibition ability of CaO NPs synthesized from both of clamshells and limestone is evident in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, which demonstrates the effect of the increase in the concentration of CaO NPs toward corrosion inhibition and that of HCl toward corrosion promotion. Between the two sources used to obtain CaO NPs, the corrosion inhibition is more significant with CaO NPs obtained from limestone that from clamshells although the difference is not signicant. Moreover, zero mass loss, \u003cem\u003ei.e\u003c/em\u003e. excellent corrosion inhibition is observed in 0.25 M HCl with 0.10 M solution of CaO synthesized from clamshells while a solution of 0.025 M CaO synthesized from limestone provides similar inbitory action. The reactive corrosion inhibition species in this system is Ca\u003csup\u003e2+\u003c/sup\u003e ions which are formed when CaO is mixed with HCl solution.\u003c/p\u003e\u003cp\u003eBecause of their size and high surface energy, CaO particles at the nanoscale may possess special chemical characteristics. By stabilizing Ca\u003csup\u003e2+\u003c/sup\u003e ions in solution, these particles can improve surface interaction with SS Grade 202 and possibly accelerate the development of a corrosion-resistant protective layer.The dissolved Ca\u003csup\u003e2+\u003c/sup\u003e can contribute more successfully to the formation of a strong passive layer on Grade SS Grade 202 when the CaO particles are smaller. Because of its higher rate of dissolution and shorter ionic interaction distances, nano CaO may promote the formation of a more homogeneous and tightly bound passivation layer.Therefore, even if CaO dissolves in HCl to form Ca\u003csup\u003e2\u003c/sup\u003e⁺ ions, the rate at which these ions are released and their ability to interact with the metal surface will determine how effective the corrosion inhibition of SS Grade 202. Concluding CaO synthesized from limestones illustrating superior corrosion inhibition [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eCorrelating the fact of physicochemical properties like larger surface area and tunable size lead to higher effectiveness of corrosion inhibition by forming a protective passive film through adsorption and barrier mechanism to avoid exposure of metal substrate from the aggressive environment [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Corrosion Inhibition Determined by EIS\u003c/h2\u003e\u003cp\u003eSupporting the results as obtained in mass loss, CaO synthesized from both clamshells and limestone perform as superior corrosion inhibition at varing concentrations. The Nyquist plots illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e demonstrate the electrochemical impedance characteristics of SS Grade 202 in HCl solutions containing CaO NPs produced from clamshells and limestone. The semicircle's diameter in each diagram signifies charge transfer resistance (\u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e), which is directly associated with corrosion resistance. A larger semicircle signifies increased resistance and improved protection against corrosion. When comparing all diagrams, both sources of CaO improve corrosion resistance relative to the blank solution. CaO derived from clamshells displays an escalating protective effect with concentration, yet its potency seems to level off at elevated concentrations (Figire 11a and 11b). In contrast, in diagrams, limestone-derived CaO unvaryingly demonstrates greater semicircle diameters, especially at 0. 050 M, signifying a more stable and effective passivation effect. This implies that limestone-derived CaO creates a more consistent and protective barrier on the steel surface, lowering charge transfer and boosting corrosion resistance. The enhanced performance of limestone-derived CaO may be influenced by variations in purity, crystalline structure, or surface activity, which enhance adhesion and protective film formation. In summary, the assessment corroborates that limestone-derived CaO offers more efficient and lasting corrosion inhibition, establishing it as the preferred option for preventing stainless steel degradation in acidic settings.\u003c/p\u003e\u003cp\u003eThe phase angle component of the Bode plot of SS Grade 202 specimen in both HCl solution and CaO NP containing solutions show three turning points associated with three time-constants. These results lead to the presence of at least three resistor \u0026ndash; capacitor (RC) pairs in the electrochemical equivalent circuit (EEC) in both systems. Figure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea depicting bode plots correspond to 0.25 M and 0.50 M HCl conclude having two turning points or two interphases. Two turning points, representing the formation of a weak passive film at high frequencies and the charge transfer process at the metal-solution interface at low frequencies, are observed in pure HCl solutions (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea), corresponding to two time constants. Accelerated corrosion is indicated by the impedance decreasing as the HCl concentration increases. On the other hand, a third turning point\u0026mdash;which represents an intermediary process involving nanoparticle adsorption\u0026mdash;is introduced by the addition of CaO nanoparticles (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb). The passive layer is improved, corrosion resistance is greatly increased, and charge transfer rates are decreased by the CaO nanoparticles. Elevated CaO NP concentrations (0.050 M and 0.100 M) demonstrate superior surface coverage and enhanced inhibition efficiency, as demonstrated by higher phase angles and elevated impedance values throughout the entire frequency spectrum. These findings demonstrate how well CaO nanoparticles work to reduce corrosion in acidic environments.\u003c/p\u003e\u003cp\u003eEEC assest the impact of CaO passivation film of SS Grade 202 in the presence of HCl including resistances (\u003cem\u003eR\u003c/em\u003e) and capacitors (\u003cem\u003eC\u003c/em\u003e). Corresponding to phase angle diagrams, various interfaces can be merged to design respective EEC. The investigation of electrochemical impedance for SS Grade 202 in HCl was conducted using equivalent circuits to evaluate the influence of CaO nanoparticles on corrosion inhibition. In the absence of CaO, the system shows reduced polarization resistance, which suggests elevated corrosion rates. Conversely, the inclusion of CaO introduces an extra R-C element, symbolizing a protective layer that enhances the passivation of the surface. The heightened impedance values verify the efficiency of CaO in minimizing metal dissolution and enhancing corrosion resistance. The additional R-C element pair in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003eb corresponds the interface of metal-CaO passive film. Impact of \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eS\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e values on corrosion inhibitory action towards SS Grade 202 in the aggressive environment is apparent in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The influence of CaO concentration and its origin on corrosion resistance is also apparent, with limestone-derived CaO offering marginally superior protection at elevated concentrations.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\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\u003ePolarizations resistance (\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e) and solution resistance (\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e) values for SS Grade 202 when immersed in different solutions, based on the electrochemical equivalent circuits.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolution\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e / Ω\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003ep1\u003c/em\u003e\u003c/sub\u003e / Ω\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eP2\u003c/em\u003e\u003c/sub\u003e / Ω\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eP3\u003c/em\u003e\u003c/sub\u003e / Ω\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e / F\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e / F\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e / F\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHCl (0.50 M)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e--\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e\u003cp\u003e2.02\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e\u003cp\u003e2.47\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e--\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.05 M) by clamshells\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e6.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e633\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e\u003cp\u003e1.57\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;12\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e\u003cp\u003e2.49\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.54\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.10 M) by clamshells\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e7.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e723\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e\u003cp\u003e900\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;15\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e\u003cp\u003e698\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e973\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.025 M) by limestone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e545\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e\u003cp\u003e900\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;15\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e\u003cp\u003e239\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e318\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.05 M) by limestone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e6.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e649\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e\u003cp\u003e900\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;15\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e\u003cp\u003e423\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;9\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e398\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\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\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e exhibits corrosion inhibition of SS Grade 202 in the presence of CaO in aggressive environments, such as 0.50 M HCl. According to the inversely proportional relationship between corrosion potential and corrosion rate illustrates low corrosion potential feasible towards much higher corrosion inhibition efficiency. Increment of CaO concentrations illustrating superior corrosion inhibition by synthesizing both materials; clamshells and limestones. Figure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003ea depicts corrosion potential order of increased CaO from clamshells concentrations whilst much less corrosion potential from CaO same concentration synthesized from limestones. Comparison of corrosion inhibition from equal concentration of CaO NPs synthesized from both materials, CaO synthesized from limestone having lower corrosion potential can be considred as the better corrosion inhibitor synthesized source. Confronting the potential variation of CaO synthesized from both materials, the corrosion potentials are much higher from synthesized from limestone as in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003eb than that synthesized from clamshells. Moreover, electrochemical parameters determined from Tafel plots are given in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\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\u003eTabulated values for corrosion potential (\u003cem\u003eE\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e), corrosion current density (\u003cem\u003eI\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e), and corrosion rate of SS Grade 202. Slopes of the anodic branch (\u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e) and the cathodoic branch (\u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e) have also been reported.\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=\"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=\"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=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolution immersed\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(V vs. Ag/AgCl/Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eI\u003c/em\u003e\u003csub\u003ecorr\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(A cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e|b\u003csub\u003ea\u003c/sub\u003e|\u003c/p\u003e\u003cp\u003e(V/dec)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e|b\u003csub\u003ec\u003c/sub\u003e|\u003c/p\u003e\u003cp\u003e(V/dec)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCorrosion rate (mmpy)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHCl (0.50 M)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.329\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e\u003cp\u003e6.92\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.58\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.75\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.05 M) by clamshell\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.296\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e\u003cp\u003e2.14\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.52\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.35\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.10 M) by clamshell\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.252\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e\u003cp\u003e1.00\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.55\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.179\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e5.8\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.025 M) by limestone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.254\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e\u003cp\u003e4.08\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.74\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.10\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.3\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMixture of HCl (in 0.50 M) and CaO (in 0.05 M) by limestone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.252\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e\u003cp\u003e6.09\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.84\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.61\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.53\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\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\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.5 OCP measurements.\u003c/h2\u003e\u003cp\u003eApart from supporting facts for corrosion inhibition by CaO NPs from mass loss measurements, EIS measurements and Tafel slope measurements, OCP measurements illustrate prominent electrochemical properties based on varying corrosion potentials of metallic or alloy substrates. The OCP of a working electrode is an indication of the tendency of a metallic substrate to be subject to deterioration in a specific environment [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The metallic substrate can adopt toward the aggressive environment of the electrolyte by building a protective coating if the OCP continues to increase and remain stable at a fixed potential over time. Inversely proportional relationship between corrosion potential and corrosion rate can be visible illustrating higher corrosion at lower corrosion potentials.\u003c/p\u003e\u003cp\u003eAt both HCl concentrations in the absence of CaO NPs, low open circuit potentials can be observed which led to higher corrosion rate (Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e). Having low corrosion potentials for HCl 0.50 M, when compared to 0.25 M HCl, confirms the corrosion promoting behavior of HCl towards SS 202. Further, CaO NPs synthesized from limestone demonstrates higher corrosion potentials having low corrosion rate than those synthesized from clamshells due to high surface area; being low nano scale particles.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4.0 Conclusion","content":"\u003cp\u003eCaO synthesized from both limestone and clamshells depicts higher effectiveness corrosion inhibition towards SS Grade 202 in the presence of aggressive environment such as HCl. Additionally, Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e acts as a corrosion enhancer for SS Grade 202, showing increased mass loss in environments with a high concentration of Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e. Based on the mass loss technique, EIS, EEC, and Tafel graphs, CaO nanoparticles significantly contribute to improving the corrosion resistance of SS Grade 202. Limestone-derived CaO NPs consisting average particle size of 4.3 nm leading to higher surface area than that of in clamshells-derived CaO NPs. In exposure of 0.50 M HCl, in the presence of 0.05 M CaO synthesized from limestone illustrating 99.12% inhibition efficiency with a corrosion rate of 3.53\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e mmpy whilst, clamshells-derived CaO at same concentration having 69.15% inhibition efficiency with a corrosion rate of 1.24 mmpy. A straighten correlation of corrosion with H\u003csub\u003e3\u003c/sub\u003eO\u003csup\u003e+\u003c/sup\u003e depicting a feasible corrosion mechanism of CaO NPs. Both CaO derived by limestone and clamshells having much higher corrosion potentials than that of absence of CaO. Thus, study denotes not only the impact of CaO NPs derived from natural materials led to a sustainable corrosion inhibition outcome, but also utilize the modifications of existing polymer coatings as synergistic effect.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eNPs\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eNanoparticles\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eEIS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eElectrochemical impedance spectroscopy\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eIE\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eInhibition efficiency\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eOCP\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eOpen circuit potentials\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eR\u003csub\u003eP\u003c/sub\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ePolarization resistance\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eR\u003csub\u003eS\u003c/sub\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eSolution resistance\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eStainless steel\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflicts of Interest\u003c/h2\u003e\u003cp\u003eThe authors declare that there are no conflicts of interest.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eConsent for publication\u003c/h2\u003e\u003cp\u003eAll authors have given the consent for the publication of the manuscript and the materials incorporated.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e\u003cp\u003eNot applicable. This research did not involve any human or animal subjects.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthor N. Priyantha contributed to the conceptualization of the study, funding acquisition, investigation and supervision. Data curation, data analysis, and writing the original draft of the manuscript were done by M.H.N. Revon. Both authors contributed to reviewing and editing of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eSpecial appreciation for the immense support provided by the Department of Chemistry, Faculty of Science, University of Peradeniya, Sri Lanka.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that supports this study will be shared upon reasonable request to the corresponding author; Namal Priyantha. ([email protected]).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAfshari F, Ghomi ER, Dinari M, Ramakrishna S. Recent advances on the corrosion inhibition behavior of Schiff base compounds on mild steel in acidic media. Chem Select. 2023;8(9):24\u0026ndash;30. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/slct.202203231\u003c/span\u003e\u003cspan address=\"10.1002/slct.202203231\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAl-Amiery AA, Mohamad AB, Kadhum AAH, Shaker LM, Isahak WNRW, Takriff MS. Experimental and theoretical study on the corrosion inhibition of mild steel by nonanedioic acid derivative in hydrochloric acid solution. Sci Rep. 2022;12(1):4705\u0026ndash;26. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-022-08146-8\u003c/span\u003e\u003cspan address=\"10.1038/s41598-022-08146-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlaoui LM, Kertit S, Bellaouchou A, Guenbour A, Benbachir A, Hammouti B. Phosphate of aluminum as corrosion inhibitor for steel in H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e. Portugaliae Electrochim Acta. 2007;26(4):339\u0026ndash;47. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4152/pea.200804339\u003c/span\u003e\u003cspan address=\"10.4152/pea.200804339\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDesai PD, Pawar CB, Avhad MS, More AP. Corrosion inhibitors for carbon steel: A review. Vietnam J Chem. 2022;61(1):15\u0026ndash;42. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/vjch.202200111\u003c/span\u003e\u003cspan address=\"10.1002/vjch.202200111\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKonovalova V. (2021). The effect of temperature on the corrosion rate of iron-carbon alloys. \u003cem\u003eMaterials Today: Proceedings\u003c/em\u003e, 38(4), 1326\u0026ndash;1329. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.matpr.2020.08.094\u003c/span\u003e\u003cspan address=\"10.1016/j.matpr.2020.08.094\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVerma C, Quraishi MA, Ebenso E, Hussain CM. Recent developments in sustainable corrosion inhibitors: Design, performance, and industrial scale applications. Mater Adv. 2021;2(12):3806\u0026ndash;50. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/d0ma00681e\u003c/span\u003e\u003cspan address=\"10.1039/d0ma00681e\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNazari MH, Zhang Y, Mahmoodi A, Xu G, Yu J, Wu J, Shi X. Nanocomposite organic coatings for corrosion protection of metals: A review of recent advances. Prog Org Coat. 2022;162:106573\u0026ndash;93. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.porgcoat.2021.106573\u003c/span\u003e\u003cspan address=\"10.1016/j.porgcoat.2021.106573\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchino AD. Manufacturing and applications of Stainless Steels. Metals. 2020;10(3):327\u0026ndash;40. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/met10030327\u003c/span\u003e\u003cspan address=\"10.3390/met10030327\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHong T, Nagumo M. The effect of chloride concentration on early stages of pitting for type 304 stainless steel revealed by the AC impedance method. Corros Sci. 1997;39(2):285\u0026ndash;93. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/s0010-938x(96)00127-8\u003c/span\u003e\u003cspan address=\"10.1016/s0010-938x(96)00127-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRam\u0026oacute;n J, Mart\u0026iacute;nez I, Gand\u0026iacute;a-Romero J, Soto J. Improved Tafel-based potentiostatic approach for corrosion rate monitoring of reinforcing steel. J Nondestr Eval. 2022;41(4):70\u0026ndash;95. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10921-022-00903-z\u003c/span\u003e\u003cspan address=\"10.1007/s10921-022-00903-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKarunanithi SP, Arasappan RK, Nallathambi SS. An overview on additive manufacturing of duplex stainless steels: Microstructure, mechanical properties, corrosion resistance, postheat treatment, and future perspectives. Steel Res Int. 2024;95(12):2400463\u0026ndash;83. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/srin.202400463\u003c/span\u003e\u003cspan address=\"10.1002/srin.202400463\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeo J, Lee SY, Lee J, Alfantazi A, Cho SO. Improvement of corrosion resistance of stainless steel welded joint using a nanostructured oxide layer. Nanomaterials. 2021;11(4):838\u0026ndash;51. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/nano11040838\u003c/span\u003e\u003cspan address=\"10.3390/nano11040838\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKhadom AA. Kinetics and synergistic effect of iodide ion and naphthylamine for the inhibition of corrosion reaction of mild steel in hydrochloric acid. Reaction Kinetics Mech Catal. 2015;115(2):463\u0026ndash;81. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11144-015-0873-9\u003c/span\u003e\u003cspan address=\"10.1007/s11144-015-0873-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim HJ, Hong JS, Choi JH, Han GS, Jung HS. Effect of phosphate ions on the formation of iron oxide/hydroxide as a stabilizer. J Solid State Chem. 2022;305:122688\u0026ndash;122688. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jssc.2021.122688\u003c/span\u003e\u003cspan address=\"10.1016/j.jssc.2021.122688\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGu F, Zhang Y, Su Z, Tu Y, Liu S, Jiang T. Recovery of chromium from chromium-bearing slags produced in the stainless-steel smelting: A review. J Clean Prod. 2021;296:126467\u0026ndash;88. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jclepro.2021.126467\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2021.126467\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHong T, Nagumo M. The effect of chloride concentration on early stages of pitting for type 304 stainless steel revealed by the AC impedance method. Corros Sci. 1997;39(2):285\u0026ndash;93. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/s0010-938x(96)00127-8\u003c/span\u003e\u003cspan address=\"10.1016/s0010-938x(96)00127-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRevon MHN, Priyantha N. Interference of Solution Constituents on Corrosion Inhibition of Phosphate Species on Grade 202 Stainless Steel. Discover Chem. 2024. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.21203/rs.3.rs-5077929/v1\u003c/span\u003e\u003cspan address=\"10.21203/rs.3.rs-5077929/v1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMandal S, Singh JK, Lee D-E, Park T. Effect of phosphate-based inhibitor on corrosion kinetics and mechanism for formation of passive film onto the steel rebar in chloride-containing pore solution. Materials. 2020;13(16):3642\u0026ndash;66. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/ma13163642\u003c/span\u003e\u003cspan address=\"10.3390/ma13163642\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang J, Lu X, Zhang J, Zhang L, Zhu C, Zhang Y, Wu T. Corrosion-inhibition effect of different phosphate compounds for carbon steel in chloride-contaminated mortars. Int J Electrochem Sci. 2019;14(9):8601\u0026ndash;10. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.20964/2019.09.29\u003c/span\u003e\u003cspan address=\"10.20964/2019.09.29\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim HJ, Hong JS, Choi JH, Han GS, Jung HS. Effect of phosphate ions on the formation of iron oxide/hydroxide as a stabilizer. J Solid State Chem. 2022;305:122688\u0026ndash;122688. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jssc.2021.122688\u003c/span\u003e\u003cspan address=\"10.1016/j.jssc.2021.122688\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePriyantha N, Jayasingha JMS, Wijesooriya WMGS. Inhibitive action of selected model compounds of eugenol on mild steel corrosion in salty medium. Prot Met Phys Chem Surf. 2021;57(2):412\u0026ndash;21. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1134/s2070205121010159\u003c/span\u003e\u003cspan address=\"10.1134/s2070205121010159\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePriyantha N, Jayaweera P, Macdonald DD, Sun A. An electrochemical impedance study of Alloy 22 in NaCl brine at elevated temperature. I. Corrosion behavior. J Electroanal Chem. 2004;572(2):409\u0026ndash;19. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jelechem.2004.06.031\u003c/span\u003e\u003cspan address=\"10.1016/j.jelechem.2004.06.031\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMacdonald DD, Priyantha N, Jayaweera P, Engelhardt G, Davydov A. The localized corrosion of Alloy 22 in simulated HLNW environments. Corrosion. 2004;61(9):857\u0026ndash;71. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5006/1.3280655\u003c/span\u003e\u003cspan address=\"10.5006/1.3280655\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e202 Stainless Steel: Composition, Properties, Applications, Processes, and More - SteelPRO Group. (2024, October 6). SteelPro. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://steelprogroup.com/stainless-steel/grades/grade-202/\u003c/span\u003e\u003cspan address=\"https://steelprogroup.com/stainless-steel/grades/grade-202/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKumar S, Singh S, Narasimhappa P, Varshney R, Singh J, Khan NA, Zahmatkesh S, Ramamurthy PC, Shehata N, Kiran GN, Sunil K. Green and sustainable synthesis of CaO nanoparticles: Its solicitation as a sensor material and electrochemical detection of urea. Sci Rep. 2023;13(1):19995\u0026ndash;20007. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-023-46728-2\\\u003c/span\u003e\u003cspan address=\"10.1038/s41598-023-46728-2\\\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSuprapto S, Fauziah TR, Sangi MS, Oetami TP, Qoniah I, Prasetyoko D. Calcium oxide from limestone as solid base catalyst in transesterification of reutealis trisperma oil. Indonesian J Chem. 2018;16(2):208\u0026ndash;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.22146/ijc.21165\u003c/span\u003e\u003cspan address=\"10.22146/ijc.21165\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlaoui LM, Kertit S, Bellaouchou A, Guenbour A, Benbachir A, Hammouti B. Phosphate of aluminum as corrosion inhibitor for steel in H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e. Portugaliae Electrochim Acta. 2007;26(4):339\u0026ndash;47. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4152/pea.200804339\u003c/span\u003e\u003cspan address=\"10.4152/pea.200804339\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShwetha KM, Praveen PBM, Devendra BK. A review on corrosion inhibitors: types, mechanisms, electrochemical analysis, corrosion rate and efficiency of corrosion inhibitors on mild steel in an acidic environment. Results Surf Interfaces. 2024;16:100258\u0026ndash;73. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.rsurfi.2024.100258\u003c/span\u003e\u003cspan address=\"10.1016/j.rsurfi.2024.100258\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBenabdellah M, Benkaddour M, Hammouti B, Bendahhou B, Aouniti A. Inhibition of steel corrosion in 2 M H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e by artemisia oil. Appl Surf Sci. 2006;252(18):6212\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.apsusc.2005.08.030\u003c/span\u003e\u003cspan address=\"10.1016/j.apsusc.2005.08.030\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBirla MS, Gabriel BI, Venkatraman MS, Cole IS, Moorthy GC, Emmanuel B. (2022). Theory of impedance for initial corrosion of metals under a thin electrolyte layer: a coupled charge transfer-diffusion model. \u003cem\u003eJournal of Chemical Sciences/Proceedings of the Indian Academy of Sciences. Chemical sciences\u003c/em\u003e, 134(1), 4\u0026ndash;10. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s12039-021-02025-x\u003c/span\u003e\u003cspan address=\"10.1007/s12039-021-02025-x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRam\u0026oacute;n J, Mart\u0026iacute;nez I, Gand\u0026iacute;a-Romero J, Soto J. Improved Tafel-based potentiostatic approach for corrosion rate monitoring of reinforcing steel. J Nondestr Eval. 2022;41(4):70\u0026ndash;95. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10921-022-00903-z\u003c/span\u003e\u003cspan address=\"10.1007/s10921-022-00903-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eScialla S, Carella F, Dapporto M, Sprio S, Piancastelli A, Palazzo B, Adamiano A, Degli Esposti L, Iafisco M, Piccirillo C. Mussel shell-derived macroporous 3D scaffold: Characterization and optimization study of a bioceramic from the circular economy. Mar Drugs. 2020;18(6):309\u0026ndash;24. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/md18060309\u003c/span\u003e\u003cspan address=\"10.3390/md18060309\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVijai KA, Reshma M, Kannan M, Muthamil Selvan S, Chaturvedi S, Shalan AE, Govindaraju K. Preparation and characterization of calcium oxide nanoparticles from marine molluscan shell waste as nutrient source for plant growth. J Nanostructure Chem. 2021;11(2):161\u0026ndash;71. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s40097-020-00376-4\u003c/span\u003e\u003cspan address=\"10.1007/s40097-020-00376-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKhalil, Rusli RK, and Andri. the effects of calcination on mineral composition and physical properties of limestones and oyster shells derived from different sources. World\u0026rsquo;s Veterinary J. 2021;11(4):578\u0026ndash;86. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.54203/scil.2021.wvj73\u003c/span\u003e\u003cspan address=\"10.54203/scil.2021.wvj73\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePardo A, Otero E, Merino MC, L\u0026oacute;pez MD, Utrilla MV, Moreno F. Influence of pH and chloride concentration on the pitting and crevice corrosion behavior of high-alloy stainless steels. Corrosion. 2000;56(4):411\u0026ndash;8. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5006/1.3280545\u003c/span\u003e\u003cspan address=\"10.5006/1.3280545\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eScharfstein LR, Brindley WF. Chloride stress corrosion cracking of austenitic stainless steel\u0026mdash;effect of temperature and pH. Corrosion. 1958;14(12):60\u0026ndash;4. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5006/0010-9312-14.12.60\u003c/span\u003e\u003cspan address=\"10.5006/0010-9312-14.12.60\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShao HB, Wang JM, Zhang Z, Zhang JQ, Cao CN. The cooperative effect of calcium ions and tartrate ions on the corrosion inhibition of pure aluminum in an alkaline solution. Mater Chem Phys. 2002;77(2):305\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/s0254-0584(02)00006-8\u003c/span\u003e\u003cspan address=\"10.1016/s0254-0584(02)00006-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNam ND, Bian MZ, Forsyth M, Seter M, Tan M, Shin KS. Effect of calcium oxide on the corrosion behaviour of AZ91 magnesium alloy. Corros Sci. 2012;64:263\u0026ndash;71. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.corsci.2012.07.026\u003c/span\u003e\u003cspan address=\"10.1016/j.corsci.2012.07.026\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlao AO, Popoola AP, Sanni O. The influence of nanoparticle inhibitors on the corrosion protection of some industrial metals: A Review. J Bio- Tribo-Corrosion. 2022b;8(3):68\u0026ndash;83. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s40735-022-00665-1\u003c/span\u003e\u003cspan address=\"10.1007/s40735-022-00665-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSenthooran R, Revon MHN, Priyantha N. Cinnamon leaf extract as an effective inhibitor for mild steel corrosion in pickling bath environments. Discover Chem. 2025;2(1):18\u0026ndash;33. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s44371-025-00083-5\u003c/span\u003e\u003cspan address=\"10.1007/s44371-025-00083-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-electrochemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Electrochemistry](https://link.springer.com/journal/44373)","snPcode":"44373","submissionUrl":"https://submission.nature.com/new-submission/44373/3","title":"Discover Electrochemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Corrosion rate, mass loss, Nyquist plots, open circuit potential, Tafel plots","lastPublishedDoi":"10.21203/rs.3.rs-7479462/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7479462/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGrade 202 Stainless Steel (SS Grade 202), an iron-based alloy with a reasonably high chromium content, is well-regarded for its notable resistance to corrosion in mild environments. Although SS Grade 202 is extensively employed in the industrial sector to develop corrosion-resistant material through further processing, effects of different chemical components present in the surrounding environment on its corrosion behavior in aggressive settings, and potential corrosion inhibitors under such conditions have not been thoroughly investigated. On the other hand, nanoparticles (NPs) inhibit corrosion by adsorption on metal surfaces thereby forming a protective barrier, thus preventing corrosive agents. NPs of CaO obtained from natural materials such as clamshells and limestone by calcination act as highly effective corrosion inhibitors due to their small size and large surface area promoting the passivation of oxide films. The ready availability of clamshells and limestone positions them as sustainable sources to produce CaO NPs, offering a cost-effective and environmentally responsible approach to corrosion protection. Corrosion rates determined with the aid of Tafel plots, depicted by CaO NPs from limestone at 0.05 M strength in the presence of 0.50 M HCl is 3.53\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e mmpy, which is much smaller when compared to CaO NPs synthesized by clamshells (1.24 mmpy).\u003c/p\u003e","manuscriptTitle":"Superior Corrosion Inhibition Activity of CaO Nanoparticles Synthesized from Natural Sources toward Grade 202 Stainless-steel in Chloride-rich Media","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-14 20:10:14","doi":"10.21203/rs.3.rs-7479462/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-15T09:30:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-07T15:39:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-06T16:48:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-05T18:29:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"55665696645797646899844114301332397047","date":"2025-11-05T16:49:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"48015730164005610725407835240108382222","date":"2025-10-31T10:30:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"227161028205467573295945459824172498848","date":"2025-10-31T09:55:46+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-13T14:31:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"70067030598192291486918222538453081080","date":"2025-10-02T03:57:30+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"16164042315743377194751676803199492540","date":"2025-09-30T06:52:51+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-30T03:54:42+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-03T07:35:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-03T07:34:56+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Electrochemistry","date":"2025-08-28T10:46:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-electrochemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Electrochemistry](https://link.springer.com/journal/44373)","snPcode":"44373","submissionUrl":"https://submission.nature.com/new-submission/44373/3","title":"Discover Electrochemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"408e2abd-a419-4f2a-b64a-41f4762441c9","owner":[],"postedDate":"October 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-05T10:02:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-14 20:10:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7479462","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7479462","identity":"rs-7479462","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}