交流电压对AZ91D镁合金阳极氧化膜层的影响

Effect of AC voltage on anodic film of AZ91D magnesium alloy

在含有硅酸钠和硅溶胶的氧化溶液体系中,利用工频交流电源对AZ91D镁合金材料表面进行阳极氧化处理,同时探讨氧化电压对膜层表面形貌、生长速率和耐腐蚀性能等的影响规律。结果表明:氧化过程存在一个明显的临界电压值(170V),在电压大于170V阳极氧化反应剧烈、氧化电流增大、试样表面出现弧光放电。当电压小于170V时,镁合金表面则以均匀的桔黄色火花放电,获得的氧化膜层表面光滑、均匀、致密,而且膜层的生长速率和耐腐蚀性随着电压的增加而增大;当电压超过这个临界电压值时,获得的氧化膜层表面变得粗糙,其生长速率大幅提高,但膜层的耐腐蚀性能下降。

The anodic films on AZ91D magnesium alloy were prepared in the electrolyte of Na2SiO3 and silica sol by AC sources. The effect of anodic voltage on the surface morphologies, growth rate and corrosion resistance of anodic films was investigated. The results show that the anodic reaction is rapid and the current increases quickly and the specimen＇s surface is bestrewed with arc discharge when the anodic voltage exceeds 170 V. When the anodic voltage is less than 170 V, bisque sparks appear on the surface of magnesium alloy uniformly. The anodic films are smooth, uniformity and compact. Moreover, the growth rate and corrosion resistance of the anodic films is improved with increasing anodi~ voltage. When the anodic voltage is more than 170 V, the anodic films become coarse and their corrosion resistance is worse though their growth rate is extremely increased.