Effects of current density on coating kinetic and micro-structure of microarc oxidation coatings fabricated on pure aluminum

Microarc oxidation (MAO) of industrial pure aluminum at different anodizing current densities in sodium metasilicate/potassium hydroxide electrolytes has been studied, with condition of equal electric charge in the MAO process. The cell voltage evolution and the coating growth rate are investigated. Meanwhile, the influence of current density on microstructure has also been demonstrated. It has been found that the properties, such as anode reaction, coating thickness, surface morphology of the anodizing coating prepared by micro-arc oxidation are closely correlative with anodizing current density. Mirodischarges are generated only when the current density up to some value. Higher current density allows the sparking voltage to be easily reached and are the most beneficial for coating production. Meanwhile, the size of micropore in coatings increases with current density.