EDTA对AZ91D镁合金锡酸盐转化膜形貌与性能的影响

Effect of EDTA on morphology and properties of stannate conversion coating on AZ91D magnesium alloy

采用化学转化处理的方法,在AZ91D镁合金基体表面制备锡酸盐转化膜。重点研究了乙二胺四乙酸(EDTA)对转化膜形貌及相组成的影响。采用极化曲线及交流阻抗对转化膜的耐蚀性进行了测试。结果表明,锡酸盐转化膜由细小的球形颗粒堆积而成,在转化液中加入EDTA后获得的转化膜的致密性大幅度提高、裂纹数量明显减少,膜层平均厚度约为2~3μm,且与基体结合较好。膜层的主要成分为Mg Sn O3·3H2O晶体。加入EDTA后获得的转化膜的耐腐蚀性能较空白基体有明显的提高。

Stannate conversion coating on AZ91 D magnesium alloy was prepared by using chemical conversion method. The effect of EDTA on the morphology and phase composition of the stannate conversion coating was studied. Corrosion resistance of the coating was investigated by polarization curve and electrochemical impedance spectrum. The results show that the stannate conversion coating is accumulated by many small spherical particles. The coating obtained from the solution with EDTA is more compact and had higher corrosion resistance. Moreover,the coating mainly composed of Mg Sn O3·3H2O crystals bonds well with the substrate.