Effect of constituents of electrolyte and operating condition on micro-arc oxidation process of Mg alloys

Magnesium alloys were treated with micro-arc oxidation in a solution containing NaAlO₂ at a constant applied current density. The effect of concentration of NaAlO₂, glycerol, NaF in electrolyte and current density and oxidation time on voltage-time response of micro-arc oxidation process and coating thickness was also investigated. The results showed that sparks could be seen at the anode surface when the electrolyte only contained NaAlO₂, the addition of glycerol can obviously restrain point discharge, the addition of NaF increased the coating thickness considerably. With the increase of the current density, ignition time of micro-arc oxidation become shorter. While the break voltage had no obvious change, and coating thickness increased obviously. The surface morphology of micro-arc oxidation coating was observed by scanning electron microscopy (SEM). The results showed that obvious pores and discharged tunnels which were melting and combined together can be seen on the coating surface.