Effect of Current Density on Ceramic Coating Prepared by Micro-arc Oxidation on 6061 Aluminum Alloy

Micro-arc oxidation coating on 6061 aluminum alloy was prepared in a Na2SiO3containing electrolyte by a constant current control mode, and the effect of current density on the microstructure and performance of micro-arc oxidation ceramic coating was studied by a series of tests. Results for the above coatings show that their thickness and surface roughness increase with the increasing current density, however, their corrosion resistance decrease, and their hardness increases first and then decreases with the increasing current density. The ceramic coatings are mainly composed of α-Al2O3and γ-Al2O3. As a comparison, a novel current control method was adopted to prepare a micro-arc oxidation coating. Accordingly, the amount of micro-cracks was significantly reduced, and the corrosion resistance was obviously enhanced for the coating prepared by the new mode.