不同锌材的三价铬钝化效果

Effect of zinc substrate on properties of trivalent chromium passive film

分别对纯锌片、钢铁镀锌片及含杂质锌片3种锌材进行三价铬钝化处理,钝化液组成及工艺条件为：硝酸铬50 g/L,硝酸钠25-55 g/L,柠檬酸25-50 g/L,氯化钠70-80 g/L,硫酸钴25-50 g/L,室温,pH 2.0,时间30-90 s。对比了不同锌材表面钝化膜的外观、金相形貌及耐蚀性等性能。结果表明,三价铬钝化处理着色和耐蚀性与锌材表面状态和组成成分有关,钝化过程产生的金属杂质离子对钝化膜的性能产生不良影响。

The pure zinc sheet,galvanized steel sheet and impure zinc sheet were separately treated by trivalent chromium passivation.The bath composition and operation conditions are as follows： chromic nitrate 50 g/L,sodium nitrate 25-30 g/L,citric acid 25-50 g/L,sodium chloride 70-80 g/L,cobaltous sulfate 25-50 g/L,room temperature,pH 2.0,and time 30-90 s.The appearance,metallographic morphology and corrosion resistance of passive films on different substrates were characterized and compared to each other.Results showed that the surface state and composition of zinc substrate influences coloring and corrosion resistance of passive film.The metal impurities produced during the passivation cause adverse effect on properties of passive film.