Corrosion resistance of micro-arc oxidized ceramic coating on cast hypereutectic alloy

The corrosion resistance of the micro-arc oxidation (MAO) ceramic coating on a cast Al-13Si-5Cu alloy was investigated using various electrochemical methods including electrochemical impedance spectroscopy (EIS) and polarization curves. Microstructures of MAO ceramic coating were studied by SEM, and the influence of microscopic patterns on corrosion resistance was analyzed. The corrosion resistance of the aluminum alloy can be improved significantly by MAO process owing to increasing impedance and corrosion potential and decreasing corrosion current, and the ceramic coatings are composed of loose layer, compact layer and transition layer, which improve the corrosion resistance. The corrosin resistance is determined by the thickness of the compact layer and is not proportional to the total thickness of MAO, though the latter is one of the important factors influencing the corrosin resistance.