Abstract: According to the self-catalytic effect of chloride ion in corrosion process, a new method based on Ag₂SO₄ as corrosion inhibitor was developed to reduce local corrosion. The corrosion inhibition effect of Ag₂SO₄ on Alloy690 was studied in 0.005 mol·L^-1 NaCl solution by using Tafel polarization curves, electrochemical impedance spectroscopy(EIS) and X-ray photoelectron spectroscopy(XPS). The corrosion current density was greatly decreased. This indicated that (AgCl₂)^- or (AgCl₃)^2- between silver ion and chloride ion were formed to decrease activity of chlorine ion in corrosion solution. The adsorption of the complex compound would change the double-layer structure from two layers to three layers, inhibiting the anodic oxidation process of Alloy690. With the increase of concentration of Ag₂SO₄, equilibrium potential would rise, and capacitance of the solid/liquid interface would decrease. Better inhibition effect than other cases could be achieved when the concentration of silver sulfate and sodium chloride ratio equaled to 0.2. Therefore, silver sulfate is a good corrosion inhibition for Alloy690 in chloride solution.

Key words: Alloy690, corrosion, electrolytes, interface, inhibitor

摘要： 针对Alloy690在局部腐蚀过程中氯离子的自催化腐蚀作用，提出了利用Ag₂SO₄作为缓蚀剂防止氯离子对Alloy690的局部腐蚀。首先利用Tafel极化曲线和电化学阻抗谱，分析了将不同浓度的Ag₂SO₄加入到0.005 mol·L^-1的NaCl 溶液对Alloy690的缓蚀效率和表面结构的影响；然后通过X射线光电子能谱（XPS）对样品表面钝化膜的组成进行了分析，并与电化学阻抗谱分析结果进行了对比。研究结果表明：在Ag₂SO₄浓度较低时，它与氯离子形成络合物可有效降低腐蚀溶液中氯离子的活动性，并且这些络合物会覆盖在Alloy690表面，抑制了Alloy 690的阳极氧化过程，改变了电极表面双电层结构，有良好的缓蚀效果。

关键词: Alloy690, 腐蚀, 电解质, 界面, 缓蚀剂