电镀锌稀土转化膜在5%NaCl溶液中耐蚀性能及耐蚀机理的研究

通过SEM,XPS,XRD分析稀土转化膜形貌、结构及物相,由浸泡实验、中性盐雾实验、电化学测量电化学参数,对比镀锌层、稀土转化膜及低铬酸盐转化膜样品的耐蚀性能,并计算稀土转化膜在5%NaCl溶液中的腐蚀动力学参数。结果表明:稀土转化膜是由微小颗粒堆积而成的完整、细密的锌和铈氧化物及氢氧化物的复合膜层,该膜层对基体镀锌层的覆盖性较好,阻碍了O2的传输和电子的传递,对腐蚀的阴、阳极反应均有不同程度的抑制,降低腐蚀动力,有效地保护了基体不受腐蚀介质的侵蚀,可有效提高镀锌层的耐蚀性能,其耐蚀性能优于低铬酸盐转化膜。

Study of Corrosion Resistance and Anti-corrosion Mechanism of Rare Earth Conversion Coatings on Zinc Plating in 5%NaCl Solution

The morphology,structure and phase of rare earth conversion coating were characterized by SEM,XPS and XRD.The corrosion resistance of rare earth conversion coating,zinc coating and low-chromium conversion coating were compared by immersion experiments,the neutral salt spray tests and electro-chemical testing methods.The corrosion kinetic parameters of rare earth conversion coating were measured in 5%NaCl solution.The results showed that rare earth conversion coating was formed by tiny fine particles without cracks and less defects,which was composed of zinc and cerium oxides and hydroxides,hindered O2 transmission and electronic transmission,inhibited both reactions of anodic and cathodic of corrosions,decreased corrosion kinetics and protected matrix from corrosion effectively.It improved the corrosion resistance performance of zinc plating,whose corrosion resistance was better than that of low-chromium conversion coating.