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Ce转化膜作为一种Cr转化膜的理想替代品而日益受到人们的重视,但其成膜机理还不很清楚.本文应用自行研制的扫描微参比电极技术(SMRE),原位测量经CeCl3溶液处理的2024-T3Al合金表面微区电位分布,并结合X光电子能谱(XPS)和交流阻抗谱(EIS),对Ce转化膜的成膜机理进行探讨.结果表明,在CeCl3溶液中,Ce转化膜的形成过程是Ce3+和Cl-相互竞争的动态过程.当由Cl-的不均匀吸附引起的局部腐蚀使pH升高时,Ce(OH)3就会首先在局部位置发生沉积.阴极反应过程产生的H2O2可将Ce(OH)3部分氧化成CeO2.
Ce conversion coating has been paid more and more attention as an ideal substitute of Cr conversion coating, but the mechanism of film formation is still unclear.In this paper, a self-developed scanning micro reference electrode (SMRE) Solution treatment of 2024-T3Al alloy surface micro-potential distribution, and combined with X-ray photoelectron spectroscopy (XPS) and alternating current impedance spectroscopy (EIS), the conversion mechanism of Ce film was studied. The results show that CeCl3 solution, Ce The formation process of the conversion film is a dynamic process in which Ce3 + and Cl- compete with each other. When the local corrosion caused by the inhomogeneous adsorption of Cl- causes the pH to increase, Ce (OH) 3 first deposits at a local site. H2O2 generated during the process can partially oxidize Ce (OH) 3 to CeO2.