Abstract 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.
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