Comparative study of micro-arc oxidation treatment for AM, AZ and MZ magnesium alloys

This paper introduces a novel coating process based on micro-arc oxidation (MAO) for formation of ceramic MgO layer over some newly developed magnesium alloys in an environmentally friendly electrolyte by anodization. Electrochemical corrosion testing showed that the corrosion resistance of bare AMS4429 is much better than that of AZ31HP-O and MZ due to formation of protective Nd-rich oxide layer in AMS4429 compared to less protective Al- and Zn-rich oxide films for AZ31HP-O and MZ respectively. Surprisingly, the corrosion resistance of MAO coated MZ is about 50 times higher than the bare one. The deposition, characterization and electrochemical characteristics of the fine porous MgO protective layer formed due to MAO coatings were investigated in details.