Development of corrosion and wear resistant micro-arc oxidation coating on a magnesium alloy

This study was initiated with the aim of extending the usage of magnesium alloys especially in corrosion and wear related engineering applications by coating their surfaces via micro arc oxidation (MAO). Considering the individual influence of phosphate-based and aluminate-based electrolytes on the corrosion and wear performances of the synthesized MAO coatings, respectively, AZ91 magnesium alloy has been subjected to MAO in aluminate-based reference electrolyte with and without additions of Na₃PO₄ at concentrations of 5 and 10 g/l. As opposed to dry sliding conditions, MAO coatings synthesized in the aluminate-based reference electrolyte did not provide good protection of AZ91 magnesium alloy against wear in corrosive media (0.9 wt% NaCl solution). This study revealed that, addition of 5 g/l Na₃PO₄ into this reference electrolyte was sufficient for enhanced resistance of MAO coating against chemical and mechanical degradations (i.e. corrosion-wear) without altering its features in terms of surface roughness and thickness.