镀锌层三价铬与六价铬钝化膜的性能

为了以三价铬替代镀锌层钝化溶液中的六价铬,实现镀锌工艺的清洁生产,利用中性盐雾实验(NSS)、Tafel曲线和扫描电镜对镀锌层三价铬和六价铬钝化膜的耐腐蚀性能、电化学行为、耐高温性能和表面结构进行了比较研究.NSS实验结果表明,三价铬钝化膜的耐腐蚀性能高于六价铬钝化膜,NSS时间可达84 h;Tafel曲线表明,三价铬钝化膜的腐蚀速率低于六价铬钝化膜,耐高温性能则高于六价铬钝化膜;SEM照片显示,三价铬钝化膜的表面形貌为致密结构,高温处理后膜层变化不大,而六价铬钝化膜表面为疏松的网状结构.

Performance of Trivalent and Hexavalent Chromium Passivation Films Based on Zinc Plating

In order to replace the hexavalent chromium in passivation solution with trivalent chromium and achieve pollution-free production for zinc plating,the corrosion resistances,electrochemical behaviors,heat-resistant abilities and microstructures of trivalent and hexavalent chromium passivation films were studied via neutral salt spray(NSS) test,Tafel plot curves and SEM.The results of NSS test show that trivalent chromium passivation film can pass 84 h of NSS test and possesses better corrosion resistance than the hexavalent one.The Tafel plot curves indicate that trivalent chromium passivation film is of a lower corrosion rate but a higher heat-resistant ability than the hexavalent one.Moreover,the SEM micrographs show that trivalent chromium passivation film is compact even after heat treatment,while the microstructure of hexavalent chromium passivation film is loose reticular.