2-巯基苯并咪唑与L-半胱氨酸在HCl中对Q235钢的协同缓蚀效应

Synergistic Inhibition Effect of 2-Mercaptobenzimidazole and L-cysteine on Q235 Steel in HCl

目的探究2-巯基苯并咪唑(MBI)、L-半胱氨酸(L-cysteine)以及两者的混合体系在1 mol/L HCl溶液中对Q235钢的缓蚀性能。方法通过静态失重法、电化学阻抗谱以及极化曲线研究MBI与L-cysteine的最佳复配条件,并借助原子力显微镜(AFM)以及X射线光电子能谱仪(XPS)分析探究MBI、L-cysteine单独以及复配后在碳钢表面的作用机理。结果当在HCl溶液中加入5×10^(-3)mol/L的MBI时,缓蚀效率达到88.01%,而相同浓度下,L-cysteine的缓蚀效率仅达60.19%,缓蚀作用有限。当MBI和L-cysteine复配时,二者的混合体系在HCl介质中具有很好的缓蚀效果,特别是当浓度为1×10^(-3)mol/L、复配比为9∶1时,缓蚀效果达到最佳,协同效应也最明显。电化学法所得结果和失重法保持一致,且进一步表明MBI和L-cysteine的混合体系同时抑制腐蚀反应的阴、阳极过程,其中抑制阴极的效果最显著。AFM形貌图以及XPS谱图分别表明浸泡在含有MBI-L-cysteine(浓度为1×10^(-3)mol/L,复配比为9∶1)溶液中的Q235钢表面更加平整,MBI-L-cysteine在Q235钢上通过吸附形成的保护膜可以显著增强Q235钢的耐酸性。结论MBI与L-cysteine(浓度为1×10^(-3)mol/L,复配比为9∶1)在1 mol/L HCl溶液中对Q235钢有显著的协同缓蚀性能,但协同效应会随着L-cysteine的增多而逐渐消失。

Adding corrosion inhibitor is the most effective measure to protect metal surface from corrosion in acidic environment,which has the advantages of low cost,simple operation and high efficiency.This paper studies the corrosion inhibition performance of 2-mercaptobenzimidazole(MBI),L-cysteine and their mixtures on Q235 steel in 1 mol/L HCl solution,the optimal mixing conditions between MBI and L-cysteine is investigated by static weight loss method,electrochemical impedance spectroscopy and polarization curve.The corrosion inhibition mechanism of MBI and L-cysteine on the surface of carbon steel is further analyzed by atomic force microscope(AFM)and X-ray photoelectron spectrometer(XPS).The Q235 carbon steel samples that cut by a molybdenum wire cutter into 20 mm×30 mm×3 mm and 10 mm×10 mm×3 mm are polished by 120#、240#、400#、600#、800#metallographic sandpaper,then by 1200#to a mirror-smooth surface under running water.After that,rinse the metal sample with distilled water,anhydrous ethanol,acetone and dry it with cold wind.In the static weight loss experiment,soak the samples(20 mm×30 mm×3 mm)in HCl solutions without and with corrosion inhibitors for 24 hours at temperature of 30℃.After that,the removed samples are scrubbed,dry and weigh.The experimental data obtained by this method are used to calculate the inhibition efficiency.The results show when MBI is used alone at a concentration of 5×10^(-3)mol/L,the corrosion inhibition efficiency reaches 88.21%,while at the same concentration,the corrosion inhibition efficiency of L-cysteine is only 60.12%.It is worth noting that when L-cysteine is added to HCl solution containing MBI,the inhibition efficiency will increase significantly,especially when the concentration is 1×10^(-3)mol/L and the compound ratio is 9∶1,the corrosion inhibition efficiency reaches the best(95.84%),i.e the corrosion inhibition efficiency of MBI-L-cysteine at a concentration which is lower than the optimal concentration of MBI or L-cysteine used alone,is higher than their respective best corrosion inhibition efficiency.In addition,the synergy effect between MBI and L-cysteine is the most obvious.The electrochemical tests including electrochemical impedance method and potentiodynamic polarization curve method are carried out on the electrochemical work station.The results are consistent with weightlessness method,and further indicates that the mixture of 2-mercaptobenzimidazole and L-cysteine simultaneously are mixed type corrosion inhibitor that predominant cathodic control over the reaction.AFM topography and XPS spectrum respectively show the surface of Q235 immersed in solution containing MBI-L-cysteine(concentration are 1×10^(-3)mol/L,compound ratio is 9∶1)is relatively smoother,and the protective film formed by them on Q235 steel through adsorption can significantly enhance the acid resistance of Q235 steel.MBI and L-cysteine(concentration is 1×10^(-3)mol/L and the compound ratio is 9∶1)have significant synergistic corrosion inhibition performance for Q235 steel in 1 mol/L HCl solution.Their synergistic inhibition mechanism is as follows:when MBI is used alone,the corrosion inhibitor film has defects due to the limitation of the molecular structure,when L-cysteine is used in combination with MBI,L-cysteine can fully fill the defects of the MBI film because its molecules have features with smaller steric hindrance,so that the composite corrosion inhibitor film is more dense.Whereas as the amount of L-cysteine in the mixed system increases,the synergistic effect will gradually disappear.