L-半胱氨酸在柠檬酸和氨基磺酸混合介质中对碳钢的缓蚀

Inhibition of L-Cysteine on carbon steel evosion in mixed media of Citric acid and sulphamic acid

采用电化学方法测定了L-半胱氨酸对A3碳钢在柠檬酸和氨基磺酸混合溶液中腐蚀行为的影响,开路电位(OCP)测定结果显示,加入L-半胱氨酸造成开路电位下降,初始L-半胱氨酸浓度越高,开路电位越高.电化学阻抗谱(EIS)测试结果显示,加入L-半胱氨酸后腐蚀反应阻抗越小,腐蚀速率增加.等效电路表明L-半胱氨酸吸附在铁的表面后促进铁和溶液界面中铁的电化学活性,并使得铁表面保护层的厚度降低,Tafel曲线显示加入L-半胱氨酸腐蚀速率增加.吉布斯自由能计算结果显示,L-半胱氨酸和铁离子形成配合物比L-半胱氨酸吸附在碳钢表面更容易发生,导致了铁的溶出,使腐蚀加剧.

Electrochemical methods were employed to investigate the corrosion behavior of A3 carbon steel in the mixture of sulphamic acid and citric acid with or without L-cysteine. The result of open circuit potential（ OCP） showed that L-cysteine could decrease OCP,and OCP was increased with initial L-cysteine concentrations. Electrochemical impedance spectroscopy（ EIS） test results showed that corrosion resistance decreased and the corrosion rate increased after L-cysteine addition.Equivalent circuit suggested that L-cysteine could adsorb onto the surface of iron and promote electrochemical activity of iron at the solution interface which could reduce the thickness of iron surface protective layer. Tafel curves confirmed showed that corrosion rate increased after adding L-cysteine. Results of Gibbs free energy culumulation suggest that cysteine-iron complexes were morelikely to form than L-cysteine adsortion onto surface of carbon steel. As a result,iron was more likely to the dissolute and the corrosion was aggravated.