电流密度对镁合金微弧氧化过程及氧化陶瓷膜性能的影响

在含有硅酸钠、氟化钠、甘油的电解液中以恒电流方式对镁合金进行微弧氧化。考察了电流密度对放电电压、起火时间及陶瓷膜厚度的影响。利用扫描电镜观察了在不同电流密度下形成的陶瓷膜的表面形貌；通过电化学交流阻抗测量了不同电流密度下得到的陶瓷氧化膜的耐蚀性能。结果表明：在恒电流微弧氧化过程中，依据电压．时间曲线，可简单地分为电压持续增长阶段和电压基本稳定阶段，且随着电流密度的增加，曲线斜率逐渐增大：电流密度的增大，可以降低起火时间，增加陶瓷氧化膜的厚度，但对放电电压并没有明显的影响：随着电流密度的增大，陶瓷层表面微孔数量减少．孔径增大，呈现出的熔融状态更为明显；陶瓷氧化膜的耐蚀性随着电流密度的升高呈现先增强后减弱的趋势。

Effect of Current Density on Mechanism of Micro-Arc Oxidization and Property of Ceramic Coating Formed on Magnesium Alloys

Magnesium alloys were treated in a solution containing silicate, fluoride and glycerol at a constant applied current density. The effect of current density on breakdown voltage, ignition time and coating thickness was investigated. SEM was employed to examine the surface morphology of ceramic coatings formed on magnesium alloys at different applied current density, and the corrosion resistance was also measured by EIS. It was concluded that according to the Voltage-Time response, the MAO process is simply divided into gradually increasing stage and a relative stable stage. With the increase of applied current density the cell voltage increasing rate is improved, coating thickness is increased lineally and ignition time is decreased, but the breakdown voltage has no apparent variation. The number of pores is decreased with the increase of current density, but the diameters of the pores are increased; EIS results indicate that corrosion resistance of ceramic coating increase firstly, then decrease with the increase of applied current density.