AZ91D镁合金微弧氧化膜的腐蚀行为研究

利用双向全波脉冲电源对AZ91D镁合金在硅酸盐体系中进行了微弧氧化处理,通过电化学阻抗谱(EIS)测试、极化曲线分析并结合XRD和SEM等分析方法对微弧氧化处理的镁合金腐蚀行为进行了研究.结果表明,微弧氧化膜表面分布着几微米的微孔,微弧氧化膜中主要含有MgF2,Mg2SiO4和Al2O3.AZ91D镁合金经过微弧氧化处理之后,耐蚀性能明显提高,自腐蚀电流密度降低3个数量级,自腐蚀电位高出约300 mV,阻抗值高出3个数量级,研制的微弧氧化膜对镁合金具有很好的防腐保护性能.

Corrosion Behavior of Microarc-oxidation Film on AZ91D Magnesium Alloy

A microarc oxidation (MAO) film was prepared on AZ91D magnesium through an alternating current at symmetric voltage in alkaline silicate solution. The corrosion resistance of MAO films were tested by electrochemical impedance spectrum (EIS), potentiodynamic polarization. Scanning electron microscopy (SEM) was used to observe the changing of surface microstructure in experiment. The composition of MAO films and corrosion products were analyzed by X-ray diffraction (XRD). The results showed that circular micron-size pores existed on the surface of MAO film. XRD analysis indicated that the ceramic coating was a spinel phase which was composed of Mg2SiO4 and MgO. The corrosion resistance of magnesium alloy coated with MAO film was improved considerably as verified by electrochemical testing. The corrosion current density decreased nearly thousand while corrosion potential moved to positive about 300mv after surface treatment with MAO. The MAO films prepared in this paper could provide good corrosion resistance of AZ91D magnesium alloy.