Visualizing the Corrosion of N80 Steel in HCl Solution Using AIE Molecules

Visualizing the Corrosion of N80 Steel in HCl Solution Using AIE Molecules | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 11 June 2025 V1 Latest version Share on Visualizing the Corrosion of N80 Steel in HCl Solution Using AIE Molecules Authors : Xue-Hong Min , Zhi-Gang Luo , Li-Zhu Zhang , Jun-Jie Yang , Bo-Kai Liao 0000-0003-2859-8422 [email protected] , and Xing-Peng Guo Authors Info & Affiliations https://doi.org/10.22541/au.174962389.97950229/v1 Published Journal of Materials Research and Technology Version of record Peer review timeline 184 views 101 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract In this work, the TBTPY-Py aggregation-induced emission (AIE) molecules with N and S have been examined as a corrosion inhibitor for N80 mild steel in 15 wt.% HCl solution was evaluated using weight loss method and electrochemical measurements. The corrosion inhibition capability of TBTPY-Py increased with the rising concentration, and the optimal corrosion inhibition efficiency reached 96.98% at 50 mg/L. The real-time fluorescence observation combined with electrochemical impedance test revealed that the AIE intensity and corrosion inhibition efficiency increased synchronously, TBTPY-Py molecules can act as the fluorescence indicator to visualize the adsorption of TBTPY-Py molecule on metal surface. The adsorption behaviour and corrosion mechanism of inhibitor molecule were further studied using atomic force microscopy, water contact angle, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope and energy Dispersive Spectrometer. Results confirmed the chemisorption of TBTPY-Py molecules on the steel surface to form a hydrophobic protective layer, thus inhibiting metal corrosion. Visualizing the Corrosion of N80 Steel in HCl Solution Using AIE Molecules Xue-Hong Min 1 ｜Zhi-Gang Luo 2 ｜Li-Zhu Zhang 2 ｜Jun-Jie Yang 3,4 *｜Bo-Kai Liao 2 *｜Xing-Peng Guo 2, 5 1 Hubei Provincial Engineering Research Center of Racing Horse Detection and Application Transformation, Equine Science Research and Doping Control Center, Wuhan Business University, Wuhan 430056, P. R. Chin｜ 2 School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou, Guangdong, 510006, P. R. China ｜ 3 Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632, P. R. China｜ 4 Shaoguan Research Institute of Jinan University, Shaoguan 512027, P.R. China｜ 5 Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China. * Corresponding author E-mail: [email protected] ｜ [email protected] . Keywords: AIE ｜ corrosion ｜ corrosion inhibitor ｜ corrosion electrochemistry In this work, the TBTPY-Py aggregation-induced emission (AIE) molecules with N and S have been examined as a corrosion inhibitor for N80 mild steel in 15 wt.% HCl solution was evaluated using weight loss method and electrochemical measurements. The corrosion inhibition capability of TBTPY-Py increased with the rising concentration, and the optimal corrosion inhibition efficiency reached 96.98% at 50 mg/L. The real-time fluorescence observation combined with electrochemical impedance test revealed that the AIE intensity and corrosion inhibition efficiency increased synchronously, TBTPY-Py molecules can act as the fluorescence indicator to visualize the adsorption of TBTPY-Py molecule on metal surface. The adsorption behaviour and corrosion mechanism of inhibitor molecule were further studied using atomic force microscopy, water contact angle, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope and energy Dispersive Spectrometer. Results confirmed the chemisorption of TBTPY-Py molecules on the steel surface to form a hydrophobic protective layer, thus inhibiting metal corrosion. 1｜Introduction The increasing ‘low-carbon’ demand of modern society encourages numbers of research efforts on reducing cost of corrosion, which is a natural spontaneous and costly phenomenon [1]. The total annual corrosion cost in china is about 2127.8 billion RMB in 2015, representing about 3.34% of the gross domestic product (GDP) [2]. Especially in petroleum exploitation and transportation, metal pipeline is easy prone to corrosion caused by the abundance of the acids and salts in the produced liquid, and pipeline corrosion cost billions of dollars yearly all around world [3]. Many methods have been established to control the corrosion of pipeline, like coating [4], sacrificial anode [5], cathodic protection [6] and corrosion inhibitor [7], etc. The corrosion-inhibiting admixture method, as one of the most convenient corrosion control strategies, has been wildly applied in oil fields [8]. Traditional corrosion inhibitors, which largely retard metal corrosion behavior with a small dosage [9, 10], are classified into two main categories, including inorganic- and organic-type [11]. Compared with inorganic corrosion inhibitor, organic corrosion inhibitor is more popular owing to some advantages [12, 13], like easy preparation, stable property, and handling, etc. Usually, the presence of heteroatom-containing group in organic corrosion inhibitor can promote the adsorption to metal surface, thus facilitating effective anti-corrosion ability [14]. In 2001, Tang et al. [15] proposed the concept of aggregation-induced emission (AIE), which show strong light emission upon the restriction of intramolecular motions (RIM) effect. AIE luminogens can offer direct visualization tools with unique optical properties, making it promising for detection, tracing, and imaging [16, 17]. What’s more, the recently emerging second NIR window (NIR-II, 1000−1700 nm) AIE fluorophores have shown great promise for in vivo imaging applications because they provide the desired imaging resolution and depth [18]. Extending conjugation length and introducing intramolecular donor-acceptor interactions are often used to achieve longer wavelength near-infrared emission. For example, benzothiadiazole units with strong electron withdrawing groups are commonly used as π bridging units and pyridine groups as electron donating groups. Thus far, the applications of AIE fluorophores in anticorrosion mainly focus on the hydrophobic coating or paint [19-21]. Few studies have reported their function as inhibitors in solutions. In this work, a novel water-soluble AIE fluorescence molecule was synthesized and applied as corrosion inhibitor for N80 mild steel in 15 wt.% HCl solution. Based on the results of in-situ electrochemical tests, liquid-AFM imaging and some surface characterizations, including Water Contact Angle (WCA), Attenuated Total Reflection Flourier Transformed Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), the optimum corrosion inhibition efficiency can reach 95.06% at 50 mg/L and a hydrophobic protective film forms on the metal surface. The rising concentration of corrosion inhibitor accelerated the adsorption behavior of TBTPY-Py molecule and thus enhanced its anti-corrosion performance. The obtained AIE molecule can be utilized as detector to visualize the adsorption behavior during corrosion inhibition process. 2｜Results and Discussion 2.1｜Characterizations of TBTPY-Py inhibito The mass spectrometry of TBTPY-Py purified by high performance liquid chromatography was given in Figure 1a. TBTPY-Py had good water solubility benefiting from the existence of two positively charged pyridinium moieties having hydrophilic properties. Ultraviolet-visible absorption spectra of TBTPY-Py in water was acquired to know the maximum absorption wavelength (Figure 1b). To study the correlation between molecular structure and corrosion inhibition mechanism, the optimized molecular structures of TBTPY-Py, electrostatic potential (ESP) map, the highest occupied molecular orbitals (HOMO), and the lowest unoccupied molecular orbitals (LUMO) were illustrated in (Figure. 1c-f) using density functional theory (DFT) calculations. The electron density variation among the molecular structure is visualized through colored ESP maps. Red and blue parts in the electrostatic potential distribution shape (ESP, Figure 2d) represent nucleophilic and FIGURE 1 HRMS (a), UV-vis adsorption spectrum (b), the optimized geometry structure (c), ESP (d) shapes, HOMO (e), and LUMO (f) of TBTPY-Py. FIGURE 2 (a) Photoluminescence spectra of TBTPY-Py in water/THF mixtures with different THF fractions. Concentration: 10 μM; excitation wavelength: 525 nm. (b) The plot of the emission maximum and the 610 nm emission intensity versus the composition of the water/THF mixtures of TBTPY-Py. electrophilic activities of molecule, respectively. The generated ESP map elucidates the red region is mainly centred on the electronegative Nitrogen atom, accelerating the adsorption on the empty orbital of Fe atom. HOMO and LUMO images display the molecular parts of the structure possessing electron-donating and accepting abilities, respectively. As shown in Figure 2, the fluorescent properties in a mixture of tetrahydrofuran (THF) and water were investigated. We found that the fluorescence intensity of TBTPY-Py in pure THF solution is much higher than that in pure water, and the overall fluorescence intensity increased with the increase of THF volume fraction, indicating that it has AIE properties. Upon the increase of THF fraction from 20 to 40 vol%, the emission of the TBTPY-Py was dramatically weakened, which is the representative twisted intramolecular charge transfer effect. 2.2｜AIE fluorescence indicator behavior To investigate the AIE fluorescence indicator behavior of TBTPY-Py inhibitor, the fluorescence observation as well as EIS test are conducted in the same time. Figure 3a-e display the fluorescence images from metal surface during the immersion in 15 wt% HCl containing 50 mg/L TBTPY-Py. With the prolong of immersion time, fluorescence intensity increased and the surface presented stronger fluorescence characteristics at 2 h. Simultaneously, EIS tests were carried out, the non-standard semi-circles can be found in Nyquist plot (Figure 3f), which can be caused by the unevenness and roughness of metal surface. The constant phase element (CPE) is thus utilized to represent the double layer capacitance. A broad peak platform can be observed in Bode diagram, indicating a equivalent circuit diagram with two-time constants can be chosen to fitted EIS results (Figure 4). The chi-squared values (σ 2 ) are given to confirm the fitting precision. The obtained fitting parameters are listed in Table 2, including R s ( resistance of solution ) , CPE f and R f (constant phase angle element and resistance of film), CPE dl and R ct (constant phase angle element and resistance of charge transfer process). The relatively lower σ 2 values imply that the fitted data have better consistency with original experimental results [22]. The corrosion inhibition FIGURE 3 Fluorescence images of the metal surfaces after immersion in 1 mol/L HCl containing 50 mg/L TBTPY-Py at 25℃ for (a) 0 h, (b) 0.5 h, (c) 1 h, (d) 2 h, (e) 3 h; (f-h) Nyquist and Bode plots for corresponding EIS at same time interval, and (g) changes of R f and corrosion inhibitor efficiency with the immersion time. FIGURE 4 Schematic diagram of equivalent circuit diagram for EIS results. Table 1 Fitted parameters for EIS results in 1 mol/L HCl solution containing 50 mg/L TBTPY-Py for different time Time (h) 0.5 (Blank) 0.5 1 2 3 R s ( Ω ･ cm 2 ) 1.05 1.92 1.89 1.86 1.9 CPE dl -T (S n1 ･Ω -1 ･cm -2 ) 1.40×10 -5 8.29×10 -6 1.58×10 -5 1.80×10 -5 1.90×10 -5 n 1 0.92 0.95 0.98 0.96 0.96 R ct ( Ω˙cm 2 ) 2.8 11.1 38.2 51.1 67.9 CPE f -T (S n1 ･Ω -1 ･cm -2 ) 1.41×10 -3 9.08×10 -5 9.00×10 -5 9.66×10 -5 9.59×10 -5 n 2 0.56 0.7 0.73 0.71 0.78 R f ( Ω ･ cm 2 ) 15.17 448.9 512.6 547.5 501.4 σ 2 1.99×10 -4 2.61×10 -4 2.50×10 -4 4.56×10 -4 5.80×10 -4 η EIS (%) - 96.1 96.7 97 96.9 efficiency ( η EIS ) can be obtained based on the obtained charge transfer resistances in the presence (R ct ) and absence (R ct 0 ) of TBTPY-Py according to Eq. (1). \(\ \eta_{\text{EIS}}\left(\%\right)=\frac{R_{\text{ct}}-R_{\text{ct}}^{0}}{R_{\text{ct}}}\times 100\)(1) The value of CPE dl obtained with the addition of TBTPY-Py is much smaller than that in the blank solution, and it decreases with the addition of inhibitor. For example, it decreased This change can be caused by the increase in the thickness of the protective film by replacing the water molecules with the adsorbed TBTPY-Py molecules or the decrease in the dielectric constant [12]. Compared with that in the blank solution, R f increased obviously with the usage of TBTPY-Py inhibitor. Values of R f and η EIS increased with the increase of immersion time, and reached their maximum within 2 h. The quite good corresponding relationship between fluorescence intensity and R f means TBTPY-Py inhibitor molecule can act as a fluorescence indicator to visualize the adsorption. 2.3｜Corrosion inhibition performance evaluation FIGURE 5 Change of weight loss and corrosion inhibition efficiency (a), OCP curve (b), Nyquist (c), PDP (d) and Bode curves (e and f) with the addition of TBTPY-Py. Table 2 Weight loss with the addition of various concentration TBTPY-Py C (mg/L) m 1 (g) m 2 (g) ΔW (g) Corrosion rate (g·cm −2 ·d −1 ) η (%) 0 2.3547 2.2615 0.0932 13.765 - 5 2.3601 2.3433 0.0168 1.8058 80.26 10 2.3044 2.2931 0.0113 0.7586 87.88 30 2.3507 2.3445 0.0062 0.4836 93.35 50 2.3238 2.3192 0.0046 0.4281 95.06 Based on the mass loss method, the corrosion rate (ν corr ) and corrosion inhibition efficiency ( η ) can be calculated using weight loss according to Eqs. (2) and (3). \(v_{\text{corr}}=\ \frac{\mathrm{\Delta}W}{S\times t}\) (2) \(\eta=\ \frac{{v_{\text{corr}}}^{0}-\ v_{\text{corr}}}{{v_{\text{corr}}}^{0}}\ \times 100\%\) (3) Where Δ W presents the average weight loss (g) of the three specimens before (m1) and after (m2) tests, S value presents the exposed area (m 2 ), t means the immersion time (h), \(\nu_{\text{corr}}\) and \(\nu_{\text{corr}}^{0}\) correspond to the corrosion rates with and without TBTPY-Py, separately. Values of weight loss and corresponding corrosion inhibition efficiency are listed in Table 2, and Figure 5a shows the weight loss and corrosion inhibition efficiency (Table 2) with different additions of TBTPY-Py. Mass loss decreases sharply with the increase of TBTPY-Py, and the corresponding corrosion inhibition efficiency increases, for example, it increases from 80.26% to 95.06% as the concentration increases from 5 to 50 mg/L. Figure 5b displays the change of OCP with time, and values of OCP can reach a relatively stable state after 1800 s immersion. Furthermore, the OCP value shifts positively with the increase of TBTPY-Py concentration compared with that in blank solution, for example, it increases from -0.462 to -0.361 V in the absence and presence of 50 mg/L TBTPY-Py. The difference of OCP with the addition of 50 mg/L TBTPY-Py is more than 85 mV, indicating it belongs to the anodic-type Table 3 Fitted parameters for EIS results in the presence of various concentration TBTPY-Py C (mg/L) R s ( Ω ･ cm 2 ) CPE f -T (S n1 ･Ω -1 ･cm -2 ) n 1 R f ( Ω˙cm 2 ) CPE dl -T (S n1 ･Ω -1 ･cm -2 ) n 2 R ct ( Ω ･ cm 2 ) σ 2 η EIS (%) 0 1.05 1.40×10 -5 0.92 2.82 1.41×10 -3 0.56 15.17 1.99×10 -4 - 5 1.14 5.96×10 -5 0.93 8.26 3.78×10 -4 0.66 59.09 4.57×10 -3 73.37 10 1.10 2.78×10 -5 0.97 7.91 2.95×10 -4 0.66 136.80 2.13×10 -3 87.57 30 0.70 1.41×10 -5 0.98 9.39 1.39×10 -4 0.65 447.00 3.95×10 -3 96.06 50 0.64 1.45×10 -5 0.99 92.3 1.01×10 -4 0.70 472.80 1.64×10 -4 96.82 Table 4 Fitted parameters for PDP results in the presence of various concentration TBTPY-Py C (mg/L) B a (mV dec -1 ) B c (mV dec -1 ) i 0 (A/cm 2 ) E 0 (V vs. SCE) η PDP (%) 0 103.6 114.4 1.17×10 -3 -0.44 - 5 77.4 123.1 1.44×10 -4 -0.42 87.70 10 82.9 125.4 6.37×10 -5 -0.44 94.55 30 85.1 127.1 3.53×10 -5 -0.47 96.98 50 83.2 125.7 2.97×10 -5 -0.48 97.46 corrosion inhibitor [23] and can adsorb on the active site of steel [24]. The corrosion behavior at the interface between electrode and solution is then investigated using EIS technique, including the Nyquist (Figure 5c) and Bode (Figure. 5e and 5f) plots. EIS results can be fitted using the equivalent circuit diagram (Figure 4), and the corresponding results are displayed in Table 3. The value of CPE dl obtained with the addition of TBTPY-Py is much smaller than that in the blank solution, and decreases with the increase of inhibitor concentration. This change can be due to the increase in the thickness of the protective film by replacing the water molecules with the adsorbed TBTPY-Py molecules or the decrease in the dielectric constant [12]. Moreover, values of R ct in the inhibited solution is larger than that in blank solution and the corresponding η EIS increases with the increase of inhibitor concentration.Figure 5d shows the PDP curves without and with TBTPY-Py, the corresponding polarization parameters can be fitted by Tafel extrapolation and are listed in Table 4, including B a and B c (apparent anodic and cathodic Tafel slope), i 0 (corrosion current density), E 0 (corrosion potential) and the corrosion inhibition efficiency ( η PDP ) . η PDP based on fitted PDP data can be calculated using the corrosion current density in the absence (i 0 0 ) and presence ( i 0 ) of TBTPY-Py as Eq. (4). \(\eta_{\text{PDP}}\ (\%)=\ \frac{i_{0}^{0}-i^{0}}{i_{0}^{0}}\ \times 100\) (4) As shown in Table 4, the addition of TBTPY-Py causes the anodic and cathodic polarization curve branches shift to the lower corrosion current density. i 0 decreases and the corresponding η PDP increases as concentration of TBTPY-Py increases, which agree with results of weight loss and EIS tests. 2.4｜Corrosion inhibition mechanism Figure 6 displays the corroded surface morphologies in the absence and presence of TBTPY-Py. Metal surface is covered with large sum of loose corrosion products (Figure 6a), indicating metal suffered severe corrosion damage. With the addition of inhibitor, metal surface becomes smooth and a dense film forms (Figure 6b-e). Figure 6f-i show the magnified images corresponding EDS results of corrosion products in the presence of 50 mg/L TBTPY-Py. Some micron-scale ball-like corrosion product and inhibitor molecule aggregates can be found on the relatively uniform and compact film. The corresponding metal roughness are presented in Figure 7. Some uniform scratches are observed on the well-polished surface (Figure 7a), and the value of roughness decreased with the TBTPY-Py concentration, indicating TBTPY-Py can effectively retard corrosion behavior. Moreover, the value of WCA obviously increases with the concentration of TBTPY-Py (Figure 8), for example, it increased from 53.3° to 108.0° as the concentration increased from 0 to 50 mg/L, suggesting that an FIGURE 6 SEM images for corroded surface in the presence of 0 mg/L (a), 5 mg/L (b), 10 mg/L (c), 30 mg/L (d), 50 mg/L TBTPY-Py (e), (f and g) two magnified images of 50 mg/L TBTPY-Py and corresponding EDS spectra (h and i). FIGURE 7 AFM images for uncorroded (a) and corroded steel surface in the presence of 0 mg/L (b), 5 mg/L (c), 10 mg/L (d), 30 mg/L (e) and 50 mg/L TBTPY-Py (f). Figure 9 shows the 3D image for adhesion force on metal surface in the presence of different increase in the inhibitor concentration increases the hydrophobic property of metal surface thus slowing down the invasion of water-soluble ions. TBTPY-Py concentrations. When the AFM tip is away from the sample surface, the force is nearly null, with the tip approaching the surface, it will receive attractive forces. The average value for adhesion force is equal to 34 μN for 5 mg/L TBTPY-Py, and it increased to 124 μN in the presence of 50 mg/L TBTPY- FIGURE 8 WCA images for uncorroded (a) and corroded steel surface in the presence of 0 mg/L (b), 5 mg/L (c), 10 mg/L (d), 30 mg/L (e) and 50 mg/L TBTPY-Py (f). FIGURE 9 AFM force scanning 3D images for uncorroded (a) and corroded steel surface in the presence of 5 mg/L (b), 10 mg/L (c), 30 mg/L (d) and 50 mg/L TBTPY-Py (e), and average adhesion force value for each concentration (f). FIGURE 10 ATR-FTIR spectra of 50 mg/L TBTPY-Py, bare and corroded steel surface in the presence of 50 mg/L TBTPY-Py. Py. The increase in the adhesion force means the metal hydrophobicity is enhanced with the rising inhibitor concentration, which agrees with the results of WCA tests. Figure 10 display the ATR-FTIR spectra for identify the groups of corrosion products. As for pure corrosion inhibitor, we can detect 3230.64 cm -1 corresponds to the intramolecular hydrogen bond (-OH) bond stretching vibration, 1647.14 cm -1 attributes to the C=C [25], peak at 1411 cm -1 is due to the C-H bending of alkene or O-H bending from C-OH group, 1078 cm -1 denotes to C-O or C=O bending [26], 968.23 cm -1 is assigned to the C-H [27], 779.21 cm -1 is C-C bending [28], peak at 655 cm -1 is C-N [29] and peak of N-S can be found at 1418 cm -1 [30]. As for the bare metal, 3795.77 cm -1 is basic hydroxyl group [31], 3265.36 cm -1 appeared due to intermolecular hydrogen bonds [32], 1629.79 cm -1 is HOH from water [33], 671.2 cm -1 attributed to the O-H out of plane bending mode [34]. As for the corrosion product obtained for N80 carbon steel immersion in HCl solution containing 50 mg/L TBTPY-Py, 3855.56 cm -1 is the presence of adsorbed H 2 O, 3745.62 cm -1 presents the terminal OH groups [35], 3228.72 cm -1 is attributed to the strongest hydrogen bonded water [36], 1701.15 cm -1 is C=O, 1514, 1552 and 1643.29 cm -1 are denoted for the stretching vibration of C=C [37-39], 1411 cm -1 is attributed to the bending of O-H group [40], 1178.3 cm -1 is C-N stretching [41] or NO - species [42], 1085.88 and 1201.61 cm -1 demonstrates the existence of C-N (sp2) [43, 44], 979.80 cm -1 is assigned to the C-N-C [45, 46], CH 2 band is to 730.99 and 848.65 cm -1 [47, 48], 783.07 cm -1 is C-C, and 650 cm -1 is attributed to C-N. The appearance of C-N peaks proves that TBTPY-Py molecule successfully adsorbed on metal surface. FIGURE 11 XPS spectra of C 1s, O 1s, Fe 2p3/2, N 1s for corrosion products in the absence (a-c) and presence (d-g) of 50 mg/L TBTPY-Py, the total spectra (h) and element distribution (i). Results of XPS tests provide further experimental evidence, as shown in Figure 11. The main elements for corrosion products in blank solution contain 11.9% Fe, 55.3% C and 32.8% O, and it changed to 3.9% Fe, 73.3% C, 20.6% O, 1.4% N and 0.8% Cl with the addition of 50 mg/L TBTPY-Py. The difference in constituent elements confirms the adsorption of inhibitor molecule on the metal surface. As for products in blank solution, C 1s can be fitted by four peaks, 288.21, 285.11, 284.6 and 284.08 eV can be associated with C=O, C-C, adventitious C and C-H [49]. O 1s contain four peaks, 531.99, 531.1, 530.35 and 529.74 eV can be assigned to the adsorbed O 2 or H 2 O, -OH, O 2- and Fe-O bonds [50-52]. Fe 2p 3/2 peaks centered at 707.01, 710.32 and 711.84 eV can be ascribed to Fe 0 , Fe 2+ and Fe 3+ [53, 54]. As for products in solution containing 50 mg/L TBTPY-Py, C 1s peak consists of five peaks, 288.87, 288.13, 288.06 284.6 and 284.14 eV can be attributed to the presence of C=O, C-O, O-C-O, C-C and C-H [55, 56]. O 1s peak contains six peaks, 533.13, 532.09, 531.38, 530.61, 530.01 and 529.55 eV can be attributed to O-C, H 2 O, oxygen-deficient state, O=C, HO-C and the existence of lattice oxygen [57]. Fe 2p 3/2 spectrum can be deconvoluted into four nearly Gaussian distributions, centered at 711.12, 709.71, 707.63 and 706.63 eV, corresponding to co-existence of Fe 2+ and Fe 3+ [58-60]. N 1s spectrum consists of two peaks, where peaks at 399.53 eV and 400.14 can be attributed to N=C [61] and N-Fe [62] bonds. The emergence of nitrogen species indicates that TBTPY-Py chemically adsorbed on the N80 steel and this protective film retarded the attack from water soluble aggressive media [63], like H + , Cl - , etc. Figure 12 briefly shows the corrosion inhibition mechanism of TBTPY-Py molecule as the inhibitor and fluorescence indicator for N80 steel in 15 wt.% HCl solution. TBTPY-Py molecules can adsorb on metal surface through chemisorption to form a hydrophobic film, which can effectively inhibit the invasion of soluble aggressive ions. After the illumination of green light, the red emission can visualize the adsorption process of TBTPY-Py molecule on metal surface. FIGURE 12 Schematic diagram for corrosion inhibition mechanism of TBTPY-Py for N80 steel in 15 wt.% HCl solution. 3｜Conclusion In this work, we prepared and utilized the water soluble AIE TBTPY-Py molecules as a fluorescence indicator and novel corrosion inhibitor for N80 mild steel in 15 wt.% HCl solution. State of the art surface characterizations and electrochemical methods were employed to clarify the anti-corrosion and fluorescence indicator behaviors. The following conclusion can be drawn: (1) TBTPY-Py molecules can act as the fluorescence indicator to visualize the adsorption of TBTPY-Py molecule on metal surface. The AIE intensity and corrosion inhibition efficiency increased synchronously at the initial immersion. (2) The corrosion inhibition capability of TBTPY-Py increased with the rising concentration, and the optimal corrosion inhibition efficiency reached 96.98% at 50 mg/L for N80 steel in HCl solution. TBTPY-Py molecule chemically adsorbed on the metal surface to form a hydrophobic protective film, thus inhibiting the invasion of water-soluble ions. 4｜Experimental Section 4.1｜Material preparation N80 carbon steel, consisting of 0.4 wt.% C, 0.2 wt.% Si, 1.5 wt.% Mn, 0.011 wt.% P, 0.003 wt.% S, 0.02 wt.% Mo and the rest Fe, was mechanical cut into 10× 10× 5 mm. The sample was encapsulated using epoxy resin with an exposed area of 1 cm 2 and then grinded using low-to-high grades of SiC sandpaper (180, 400 and 1200 grid). The polished surfaces are cleaned using deionized water, acetone and alcohol in sequence, then dried with cold wind and stored in a vacuum desiccator for the following tests. The synthesis of TBTPY-Py started from N, N-diphenyl-4-vinylaniline, and the detailed procedures were as depicted in Figure 13, yield: 38%. All the reactions are refluxed under nitrogen. All the other solutions are prepared using analytical reagents (Sigma-Aldrich) and deionized water. FIGURE 13 Synthetic routes to TBTPY-Py corrosion inhibitor 4.2｜Weight loss test Prior weight loss test, the initial average weight of each N80 sample is weighing for three times using the analytical balance (accuracy with 0.1 mg). After corrosion for 24 h in HCl solution, the corrosion products on metal surface are removed by the acid pickling process, then cleaned by deionized water and dried using clod air. The mean values for weight after immersion tests are re-measured for thrice time. 4.3｜Electrochemical measurements Electrochemical tests, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PDP), are conducted using an electrochemical station (CS310H, Corrtest, china) in a conventional three-electrode cell, which consists of encapsulated N80 steel sample as working electrode, platinum tablet as counter electrode and saturated calomel electrode (SCE) as reference electrode. EIS and PDP tests start after OCP reaches the stable state. As for EIS test, a 5 mV sinusoidal potential versus OCP is applied in the frequency range of 10 4 ~ 10 -2 Hz. In PDP test, the scanning potential range is -0.25 to 0.25 V vs. OCP at a rate of 0.5 mV/s. Zview and Cview software are applied to analyze the experimental results of EIS and PDP, respectively. 4.4｜Characterizations The obtained TBTPY-Py was confirmed by High Resolution Mass Spectrometry, HRMS (ESI-Q-TOF, m/z), calcd for C 44 H 41 N 5 S 2+ 335.665, found 335.653. And the Ultraviolet-visible (UV) absorption spectrum of TBTPY-Py in water was acquired. Hitachi F-4600 fluorescence spectrophotometer was utilized to measure the fluorescence intensity. Real-time fluorescence images were obtained using an Olympus 1X73 fluorescence microscopy with mercury lamp as the light source and the excitation wavelength was green light. The metal surface morphologies before and after immersion tests were characterized by SEM (SU1510, Japan), and the corresponding surface hydrophobicity parameter was measured using water contact angle (WCA) tester (ZJ-7000, China). The surface adhesion force on carbon steel was research by AFM (MFP-3D, America) and the compositions for corrosion products were investigated by EDS (Oxford, US) XPS (AXIS NOVA, Japan). Acknowledgements Authors thanks to Analysis and Test Center of Guangzhou University for their technical support and the following foundations for financial supports to this work: The Natural Science Foundation of Hubei Province of China (2024AFB870); National Natural Science Foundation of China (Grant No. 52101084 and 52001080); Guangdong Basic and Applied Basic Research Foundation (Grand No. 2024A1515010905, 2024A1515030004 and 2023A1515011579); Research and development of testing standards for prohibited substances in sports horses (2024TD021). Conflict of Interests The authors declare no conflict of interests. References [1] X. Li, D. Zhang, Z. Liu, Z. Li, C. Du, C. Dong, Materials science: Share corrosion data, Nature, 527 (2015) 441-442.[2] B. Hou, X. Li, X. Ma, C. Du, D. Zhang, M. Zheng, W. Xu, D. Lu, F. Ma, The cost of corrosion in China, npj Materials Degradation, 1 (2017) 4.[3] H.R. Vanaei, A. Eslami, A. Egbewande, A review on pipeline corrosion, in-line inspection (ILI), and corrosion growth rate models, International Journal of Pressure Vessels and Piping, 149 (2017) 43-54.[4] S. Wan, H. Chen, G. Cai, B. Liao, X. Guo, Functionalization of h-BN by the exfoliation and modification of carbon dots for enhancing corrosion resistance of waterborne epoxy coating, Progress in Organic Coatings, 165 (2022) 106757.[5] X. Cao, F. Huang, C. Huang, J. Liu, Y.F. Cheng, Preparation of graphene nanoplate added zinc-rich epoxy coatings for enhanced sacrificial anode-based corrosion protection, Corrosion Science, 159 (2019) 108120.[6] S. Wu, Z. Gao, Y. Liu, W. Hu, Effect of cathodic protection potential on stress corrosion susceptibility of X80 steel, Corrosion Science, 218 (2023) 111184.[7] L. Ma, J. Wang, Y. Wang, X. Guo, S. Wu, D. Fu, D. Zhang, Enhanced active corrosion protection coatings for aluminum alloys with two corrosion inhibitors co-incorporated in nanocontainers, Corrosion Science, 208 (2022) 110663.[8] Y. Fairuzov, V. Fairuzov, Diagnosis of Internal Corrosion in Pipelines Based on Mapping Adverse Operational Conditions, in: CORROSION 2019, OnePetro, 2019.[9] B. Liao, Z. Luo, S. Wan, L. Chen, Insight into the anti-corrosion performance of Acanthopanax senticosus leaf extract as eco-friendly corrosion inhibitor for carbon steel in acidic medium, Journal of Industrial and Engineering Chemistry, 117 (2023) 238-246.[10] Q. Chen, Z. Zhou, M. Feng, J. He, Y. Xu, B. Liao, Unraveling the inhibitive performance and adsorption behavior of expired compound glycyrrhizin tablets as a novel corrosion inhibitor for copper in acidic medium, Journal of the Taiwan Institute of Chemical Engineers, 168 (2025) 105913.[11] S. Wan, T. Zhang, H. Chen, B. Liao, X. Guo, Kapok leaves extract and synergistic iodide as novel effective corrosion inhibitors for Q235 carbon steel in H 2 SO 4 medium, Industrial Crops and Products, 178 (2022) 114649.[12] Z. Zheng, J. Hu, N. Eliaz, L. Zhou, X. Yuan, X. Zhong, Mercaptopropionic acid-modified oleic imidazoline as a highly efficient corrosion inhibitor for carbon steel in CO 2 -saturated formation water, Corrosion Science, 194 (2022) 109930.[13] C.K. Nmai, Multi-functional organic corrosion inhibitor, Cement and Concrete Composites, 26 (2004) 199-207.[14] Y.-H. Chen, A. Erbe, The multiple roles of an organic corrosion inhibitor on copper investigated by a combination of electrochemistry-coupled optical in situ spectroscopies, Corrosion Science, 145 (2018) 232-238.[15] Y. Tu, Z. Zhao, J.W. Lam, B.Z. Tang, Aggregate science: much to explore in the meso world, Matter, 4 (2021) 338-349.[16] H. Wang, E. Zhao, J.W. Lam, B.Z. Tang, AIE luminogens: emission brightened by aggregation, Materials today, 18 (2015) 365-377.[17] J. Li, J. Wang, H. Li, N. Song, D. Wang, B.Z. Tang, Supramolecular materials based on AIE luminogens (AIEgens): construction and applications, Chemical Society Reviews, 49 (2020) 1144-1172.[18] Y. Duan, B. Liu, Recent advances of optical imaging in the second near‐infrared window, Advanced materials, 30 (2018) 1802394.[19] L. Wang, L. Wang, J. Wu, L. Wang, W. Cong, X. Wang, R. Hu, W. Li, M. Tebyetekerwa, B.Z. Tang, Exploring the mechanism of self-stratifying coatings with aggregation-induced emission, Progress in Organic Coatings, 159 (2021) 106448.[20] W. Lu, S. Zhang, L. Wang, C. Guo, X. Wang, D. Wang, Z.-B. Zhao, K. Yang, Y. Ma, W. Li, Understanding the role of epoxy emulsifiers in water-borne epoxy coatings with the aggregation-induced emission approach, Progress in Organic Coatings, 170 (2022) 106987.[21] L. Wang, L. Wang, X. Yang, W. Li, L. Chen, J. Tang, W. Cong, R. Hu, M. Tebyetekerwa, B. Tang, Aggregation-induced emission molecules enable characterization of superhydrophobic coatings, Progress in Organic Coatings, 163 (2022) 106633.[22] B. Liao, H. Cen, Z. Chen, X.J.C.S. Guo, Corrosion behavior of Sn-3.0 Ag-0.5 Cu alloy under chlorine-containing thin electrolyte layers, 143 (2018) 347-361.[23] K. Evans, S. Chawla, K. Sherer, J. Beavers, N. Sridhar, K. Boomer, The Passive Film Evolution of Carbon Steel in Hanford Waste Simulants, 2018.[24] Q.H. Zhang, B.S. Hou, G.A. Zhang, Inhibitive and adsorption behavior of thiadiazole derivatives on carbon steel corrosion in CO 2 -saturated oilfield produced water: Effect of substituent group on efficiency, Journal of Colloid and Interface Science, 572 (2020) 91-106.[25] N. Shukla, C. Liu, P.M. Jones, D. Weller, FTIR study of surfactant bonding to FePt nanoparticles, Journal of Magnetism and Magnetic materials, 266 (2003) 178-184.[26] N. Rajeswari, S. Selvasekarapandian, S. Karthikeyan, M. Prabu, G. Hirankumar, H. Nithya, C. Sanjeeviraja, Conductivity and dielectric properties of polyvinyl alcohol–polyvinylpyrrolidone poly blend film using non-aqueous medium, Journal of Non-Crystalline Solids, 357 (2011) 3751-3756.[27] Y. Baek, Y. Ryu, K. Yong, Structural characterization of β-SiC nanowires synthesized by direct heating method, Materials Science and Engineering: C, 26 (2006) 805-808.[28] R. Selvaraju, A. Raja, G. Thiruppathi, FT-IR spectroscopic, thermal analysis of human urinary stones and their characterization, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 137 (2015) 1397-1402.[29] V. Arjunan, S. Mohan, S. Subramanian, B.T. Gowda, Synthesis, Fourier transform infrared and Raman spectra, assignments and analysis of N-(phenyl)-and N-(chloro substituted phenyl)-2, 2-dichloroacetamides, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 60 (2004) 1141-1159.[30] F.M. Mady, S.R. Mohamed Ibrahim, Cyclodextrin-based nanosponge for improvement of solubility and oral bioavailability of Ellagic acid, Pakistan journal of pharmaceutical sciences, (2018).[31] D. Guillaume, S. Gautier, F. Alario, J. Deves, Relation between acid and catalytic properties of chlorinated gamma-alumina. a 31p Mas Nmr and ftir investigation, Oil & Gas Science and Technology, 54 (1999) 537-545.[32] Y. Hishikawa, S.-i. Inoue, J. Magoshi, T. Kondo, Novel tool for characterization of noncrystalline regions in cellulose: a FTIR deuteration monitoring and generalized two-dimensional correlation spectroscopy, Biomacromolecules, 6 (2005) 2468-2473.[33] D.V. Kozlov, E.A. Paukshtis, E.N. Savinov, The comparative studies of titanium dioxide in gas-phase ethanol photocatalytic oxidation by the FTIR in situ method, Applied Catalysis B: Environmental, 24 (2000) L7-L12.[34] D. Sajan, H. Joe, V.S. Jayakumar, J. Zaleski, Structural and electronic contributions to hyperpolarizability in methyl p-hydroxy benzoate, Journal of Molecular Structure, 785 (2006) 43-53.[35] I. Kiricsi, C. Flego, G. Pazzuconi, W.J. Parker, R. Millini, C. Perego, G. Bellussi, Progress toward understanding zeolite. beta. acidity: an IR and 27Al NMR spectroscopic study, The Journal of Physical Chemistry, 98 (1994) 4627-4634.[36] C. Sammon, C. Mura, S. Hajatdoost, J. Yarwood, ATR-FTIR study of the diffusion and interaction of water and electrolyte solutions in polymeric membranes, Journal of Molecular Liquids, 96-97 (2002) 305-315.[37] E. Gulari, K. Mckeigue, K. Ng, Raman and FTIR spectroscopy of polymerization: Bulk polymerization of methyl methacrylate styrene, Macromolecules, 17 (1984) 1822-1825.[38] C. Yuan, Z. Jin, X. Xu, Inclusion complex of astaxanthin with hydroxypropyl-β-cyclodextrin: UV, FTIR, 1H NMR and molecular modeling studies, Carbohydrate polymers, 89 (2012) 492-496.[39] P.C. Rodrigues, M.c.P. Cantão, P. Janissek, P.C. Scarpa, A.L. Mathias, L.P. Ramos, M.A. Gomes, Polyaniline/lignin blends: FTIR, MEV and electrochemical characterization, European Polymer Journal, 38 (2002) 2213-2217.[40] O. Anjos, M.G. Campos, P.C. Ruiz, P. Antunes, Application of FTIR-ATR spectroscopy to the quantification of sugar in honey, Food chemistry, 169 (2015) 218-223.[41] G. Sangeetha, An Investigation of ATR-FTIR Compatibility Studies and Preformulation Studies of Tapentadol HCl to Design and Formulate Transdermal Proniosomal Gel.[42] L. Xu, X.-S. Li, M. Crocker, Z.-S. Zhang, A.-M. Zhu, C. Shi, A study of the mechanism of low-temperature SCR of NO with NH3 on MnOx/CeO 2 , Journal of Molecular Catalysis A: Chemical, 378 (2013) 82-90.[43] J. Wei, P. Hing, Z. Mo, TEM, XPS and FTIR characterization of sputtered carbon nitride films, Surface and Interface Analysis: An International Journal devoted to the development and application of techniques for the analysis of surfaces, interfaces and thin films, 28 (1999) 208-211.[44] H. Zhang, J. Magoshi, M. Becker, J.Y. Chen, R. Matsunaga, Thermal properties of Bombyx mori silk fibers, Journal of applied polymer science, 86 (2002) 1817-1820.[45] B.C. Barja, M. dos Santos Afonso, An ATR−FTIR Study of Glyphosate and Its Fe(III) Complex in Aqueous Solution, Environmental Science & Technology, 32 (1998) 3331-3335.[46] N.E. Mircescu, M. Oltean, V. Chiş, N. Leopold, FTIR, FT-Raman, SERS and DFT study on melamine, Vibrational Spectroscopy, 62 (2012) 165-171.[47] C. Yu, J. Bao, Q. Xie, G. Shan, Y. Bao, P. Pan, Crystallization behavior and crystalline structural changes of poly (glycolic acid) investigated via temperature-variable WAXD and FTIR analysis, CrystEngComm, 18 (2016) 7894-7902.[48] R. Chércoles Asensio, M. San Andrés Moya, J.M. de la Roja, M. Gómez, Analytical characterization of polymers used in conservation and restoration by ATR-FTIR spectroscopy, Analytical and bioanalytical chemistry, 395 (2009) 2081-2096.[49] M.U. Monir, F. Khatun, A. Abd Aziz, D.-V.N. Vo, Thermal treatment of tar generated during co-gasification of coconut shell and charcoal, Journal of Cleaner Production, 256 (2020) 120305.[50] J.C. Dupin, D. Gonbeau, P. Vinatier, A. Levasseur, Systematic XPS studies of metal oxides, hydroxides and peroxides, Physical Chemistry Chemical Physics, 2 (2017).[51] G.H. Kim, H.S. Kim, H.S. Shin, B.D. Ahn, K.H. Kim, H.J. Kim, Inkjet-printed InGaZnO thin film transistor, Thin Solid Films, 517 (2009) 4007-4010.[52] J.H. Shah, A.S. Malik, A.M. Idris, S. Rasheed, H. Han, C. Li, Intrinsic photocatalytic water oxidation activity of Mn-doped ferroelectric BiFeO 3 , Chinese Journal of Catalysis, 42 (2021) 945-952.[53] K. Zhao, X. Fang, C. Cui, S. Kang, A. Zheng, Z. Zhao, Co-production of syngas and H 2 from chemical looping steam reforming of methane over anti-coking CeO2/La0.9Sr0.1Fe1−xNixO3 composite oxides, Fuel, 317 (2022) 123455.[54] Z. Peng, L. Hu, J. Shi, Z. Zheng, H. Dong, T. Wang, Gap channel carbon layer coated bimetallic CoFe phosphate as a bifunctional electrocatalyst for overall water splitting, Journal of Power Sources, 538 (2022) 231571.[55] T.I.T. Okpalugo, P. Papakonstantinou, H. Murphy, J. McLaughlin, N.M.D. Brown, High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs, Carbon, 43 (2005) 153-161.[56] C. Liu, A. Yao, K. Chen, Y. Shi, Y. Feng, P. Zhang, F. Yang, M. Liu, Z. Chen, MXene based core-shell flame retardant towards reducing fire hazards of thermoplastic polyurethane, Composites, Part B. Engineering, (2021) 226.[57] H. Wang, Y. Yang, J. Wei, L. Le, Y. Liu, C. Pan, P. Fang, R. Xiong, J. Shi, Effective photocatalytic properties of N doped Titanium dioxide nanotube arrays prepared by anodization, Reaction Kinetics, Mechanisms and Catalysis, 106 (2012) 341-353.[58] J. Tian, A. Zhang, R. Liu, W. Huang, Z. Yuan, R. Zheng, D. Wei, J. Liu, Preparation of CoS 2 supported flower-like NiFe layered double hydroxides nanospheres for high-performance supercapacitors, Journal of Colloid and Interface Science, 579 (2020) 607-618.[59] Qingyao, Wang, Rencheng, Jin, Miao, Zhang, Shanmin, Gao, Solvothermal preparation of Fe-doped TiO 2 nanotube arrays for enhancement in visible light induced photoelectrochemical performance, Journal of Alloys and Compounds, 690 (2017) 139-144.[60] B. Liao, S. Ma, S. Zhang, X. Li, R. Quan, S. Wan, X. Guo, Fructus cannabis protein extract powder as a green and high effective corrosion inhibitor for Q235 carbon steel in 1 M HCl solution, International Journal of Biological Macromolecules, 239 (2023) 124358.[61] C. Yang, W. Xu, X. Meng, X. Shi, L. Shao, X. Zeng, Z. Yang, S. Li, Y. Liu, X. Xia, A pH-responsive hydrophilic controlled release system based on ZIF-8 for self-healing anticorrosion application, Chemical Engineering Journal, 415 (2021) 128985.[62] M. Mobin, M. Shoeb, R. Aslam, P. Banerjee, Synthesis, characterisation and corrosion inhibition assessment of a novel ionic liquid-graphene oxide nanohybrid, Journal of Molecular Structure, 1262 (2022) 133027.[63] Y. Qiang, L. Guo, H. Li, X. Lan, Fabrication of environmentally friendly Losartan potassium film for corrosion inhibition of mild steel in HCl medium, Chemical Engineering Journal, 406 (2021) 126863. Water-soluble AIE-active TBTPY-Py with N and S serves as a fluorescent corrosion inhibitor for N80 steel in 15% HCl. Adsorption on the metal surface enhances both fluorescence and inhibition efficiency (96.98% at 50 mg/L). It forms a hydrophobic film via chemical adsorption, blocking corrosive ions. Synergistic anti-corrosion and real-time monitoring are achieved through combined electrochemical and surface characterization. Information & Authors Information Version history V1 Version 1 11 June 2025 Peer review timeline Published Journal of Materials Research and Technology Version of Record 1 Sep 2025 Published Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords aie corrosion corrosion electrochemistry corrosion inhibitor Authors Affiliations Xue-Hong Min Wuhan Business University Library View all articles by this author Zhi-Gang Luo Guangzhou University School of Chemistry and Chemical Engineering View all articles by this author Li-Zhu Zhang Guangzhou University School of Chemistry and Chemical Engineering View all articles by this author Jun-Jie Yang Jinan University View all articles by this author Bo-Kai Liao 0000-0003-2859-8422 [email protected] Guangzhou University School of Chemistry and Chemical Engineering View all articles by this author Xing-Peng Guo Guangzhou University School of Chemistry and Chemical Engineering View all articles by this author Metrics & Citations Metrics Article Usage 184 views 101 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Xue-Hong Min, Zhi-Gang Luo, Li-Zhu Zhang, et al. Visualizing the Corrosion of N80 Steel in HCl Solution Using AIE Molecules. 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