Incorporation of Al₂O₃ and ZrO₂ ceramics to AZ31 magnesium alloys composite coating using micro-arc oxidation method

In this research, a composite coating with Al₂O₃ and ZrO₂ particles have been applied on AZ31 magnesium alloy by micro-arc oxidation (MAO) technique. The alkaline electrolyte included a constant based composition and different composition of the Al₂O₃ and ZrO₂ additives. Microstructure observations reveal that the surface pores of composite coating reduced during addition of ZrO₂ and Al₂O₃ ceramic particles. The hardness of coating increased from about 380 for non-added to 620 MPa for Al₂O₃+ZrO₂ added coating and wear rate reduced about 8 times. Wettability of the coating increased by incorporation of Al₂O₃ and/or ZrO₂ particles while, Al₂O₃ is more effective than ZrO₂. Addition of the ceramic particles enhanced the hydrophilicity properties of surface in wettability test and a contact angle of 43° was obtained for coating including Al₂O₃+ZrO₂. The antibacterial properties of MAO coatings showed that S. aureus bacterium is more sensitive to the zirconia and alumina particle than S. typhimurium bacterium after 24 h of incubation.