Effect of current density on corrosion resistance of
micro-arc oxide coatings on magnesium alloy
(Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012, China)
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 (Ra) 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