Meng Siguang, Liu Zining, Zhao Xiaoqi, Fan Baomin, Liu Hao, Guo Mao, Hao Hua
College of Chemistry and Materials Engineering, Beijing Technology and Business University Beijing 100048 China
Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China.
RSC Adv. 2021 Sep 27;11(50):31693-31711. doi: 10.1039/d1ra04976c. eCollection 2021 Sep 21.
Sugarcane purple rind ethanolic extract (SPRE) was evaluated as an efficient corrosion inhibitor for carbon steel (C-steel) in 1 M HCl solution. Dynamic weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and frequency modulation (EFM) measurements were employed to evaluate the anticorrosive efficiency of SPRE, which was further validated by morphological and wettability analyses. The results of the weight loss tests showed that the inhibition efficiency ( ) for C-steel in HCl solution increased with an increase in the concentration of SPRE. An increase in temperature moderately impaired the anticorrosive efficacy of SPRE. The maximum of 96.2% was attained for C-steel in the inhibition system with 800 mg L SPRE at 298 K. The polarization curves indicated that SPRE simultaneously suppressed the anodic and cathodic reactions for C-steel in HCl solution, which can be categorized as a mixed-type corrosion inhibitor with a predominant anodic effect. The corrosion current density ( ) was monotonously reduced with an increase in the concentration of SPRE. The charge transfer resistance ( ) was enhanced for C-steel in the inhibition solution with a restrained capacitive property due to the adsorption of SPRE. A high temperature caused partial desorption of SPRE on the C-steel surface and a slight increase in and decrease in . However, SPRE still fully maintained its morphology and wettability at 328 K. The electrochemical kinetics of C-steel in HCl solution without and with SPRE was also supported by EFM spectra. The adsorption of SPRE conformed to the Langmuir isotherm and increased the corrosion activation energy of C-steel. Complementing the experimental observations, calculations based on density functional theory indicated that the hydroxyl-substituted pyran moiety on the carthamin (CTM) and anthocyanin (ATC) constituents in SPRE hardly contributed to its reactive activity due to their adsorption processes. Therefore, CTM and ATC exhibited imperfect parallel adsorption on the Fe (100) plane according to the molecular dynamics simulation, while anthoxanthin (ATA) and catechinic acid (CCA) constituents exhibited a flat orientation on the iron surface.
甘蔗紫皮乙醇提取物（SPRE）被评估为1 M HCl溶液中碳钢（C钢）的高效缓蚀剂。采用动态失重、动电位极化、电化学阻抗谱（EIS）和调频（EFM）测量来评估SPRE的防腐效率，并通过形态学和润湿性分析进一步验证。失重试验结果表明，HCl溶液中C钢的缓蚀效率（ ）随SPRE浓度的增加而提高。温度升高适度削弱了SPRE的防腐效果。在298 K下，800 mg L SPRE的缓蚀体系中C钢的最大缓蚀效率达到96.2%。极化曲线表明，SPRE同时抑制了HCl溶液中C钢的阳极和阴极反应，可归类为具有主要阳极效应的混合型缓蚀剂。腐蚀电流密度（ ）随SPRE浓度的增加而单调降低。由于SPRE的吸附，抑制溶液中C钢的电荷转移电阻（ ）增大，电容特性受到抑制。高温导致SPRE在C钢表面部分解吸， 略有增加， 略有降低。然而，SPRE在328 K时仍能完全保持其形态和润湿性。EFM光谱也支持了HCl溶液中有无SPRE时C钢的电化学动力学。SPRE的吸附符合Langmuir等温线，并增加了C钢的腐蚀活化能。基于密度泛函理论的计算补充了实验观察结果，表明SPRE中红花素（CTM）和花青素（ATC）成分上的羟基取代吡喃部分由于其吸附过程对其反应活性贡献不大。因此，根据分子动力学模拟，CTM和ATC在Fe（100）面上表现出不完全平行吸附，而黄酮（ATA）和儿茶酸（CCA）成分在铁表面表现出平面取向。
