Characterization of ceramic coating on ZK60 magnesium alloy prepared in a dual electrolyte system by micro-arc oxidation

Micro-arc oxidation (MAO) process was carried out in an optimized dual electrolyte system to fabricate a compact, smooth, and corrosion resistant coating on ZK60 Mg alloy. The microstructural characteristics of coating were investigated by scanning electron microscopy (SEM) coupled with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Test of mass loss was conducted at a 3.5 % NaCl solution to assess the resistance to corrosion. The bonding strength between the coating and ZK60 substrate was evaluated using scratch experiment. The results reveal that MgAl₂O₄ and MgO are the main phases of ceramic coating obtained in the dual electrolyte system. The corrosion rate of coating prepared in the optimized dual electrolyte is only 0.0061 g·m⁻²·h⁻¹, which demonstrates excellent corrosion resistance. This is mainly due to the compact, uniform coating with high bonding strength.