通过电导率测试跟踪乙烯基三乙氧基硅烷(A-151)的水解过程,然后将水解完全的A-151水解液添加到基础钝化液中进行复合钝化,研究以替代有毒铬酸盐钝化.采用中性盐雾腐蚀试验(NSS)研究了所得复合钝化膜的耐蚀性;应用SEM/EDS分析了复合钝化膜的形貌及元素组成;极化曲线和电化学阻抗测试研究了钝化膜的耐蚀性及耐蚀机理.结果表明,所得复合钝化膜72 h NSS后腐蚀面积百分比仅为4%;SEM/EDS结果显示在镀锌层表面形成了厚度约为8 μm的保护性膜层,膜的主要组成元素为Si、Mo、P和O等;极化曲线表明复合钝化膜的存在主要抑制锌腐蚀过程中的阳极反应.电化学阻抗表明,低频区复合钝化膜的阻抗值比基体锌板增加了一个数量级.

In order to replace the toxic chromate passivation,a composite passivation film was prepared on the galvanized steel by tracking the hydrolysis process of vinyl triethoxy silane(A-151) via conductivity tests and then adding the hydrolysis solution into the basic passivation bath.The corrosion resistance and mechanism of the composite passivation film were studied by neutral salt spray tests (NSS),polarization curve tests and electrochemical impedance spectroscopy (EIS).SEM/EDS were used to analyze the appearance and elements of passivated galvanized steel.The NSS results show that the corrosion area percentage of treated samples was only 4% after 72 h NSS.The SEM/EDS results indicate that a film about 8μm was formed on the galvanized steel,and the constitutes were Si,Mo,P and O.The composite passivation film blocks the anodic reaction of corrosion process.EIS results show that the total impedance of the composite film at the lowest frequency increased by more than one order of magnitude compared with the galvanized steel.