Abstract:Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na₂SiO₃ at different current densities (3, 4 and 5 A/cm²) with micro-arc oxidation process. X-ray diffractometry (XRD) results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl₂O₄ phases; in addition, the content of MgO increases with increasing the current density. The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM). The results show that the surface roughness (R_a) decreases with increasing the current density. Moreover, the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na₂SiO₃ at current density of 5 A/cm² shows the best corrosion resistance.

Key words: magnesium alloy; micro-arc oxidation; current density; corrosion resistance