Corrosion Resistance of Micro-arc Oxidation Ceramic Coating on Aluminum Alloy Surfaces

A dense oxide ceramic coating was prepared on 2A12 aluminium alloy by micro-arc oxidation in a Na2SiO3-Na2WO4-KOH-Na2EDTA electrolytic solution.Using SEM and XRD,the cross sectional morphology and phase structure of the micro-arc oxidation ceramic coating were analyzed.The microhardness of coating surface was also measured.The corrosion resistance of the micro-arc oxidation ceramic coating was tested using CS300P electrochemical corrosion workstation in 36 g/L NaCl solution.The thickness of micro-arc oxidation ceramic coating is about 4 μm.The microharness of coating surface is up to 683 HV.The phases are mainly α-Al2O3 and γ-Al2O3 in the coating.The corrosion resistance of the micro-arc oxidation ceramic coating in 36 g/L NaCl solution is enhanced remarkably,the corrosion velocity is obviously slowed down.