Excellent corrosion resistance of P and Fe modified micro-arc oxidation coating on Al alloy

The corrosion resistance of aluminum and its alloys requires improvement in some applications. In this work, a 20 μm thick compact alumina coating doping Fe and P is obtained on the substrate of LY12 Al alloy by combining micro-arc oxidation (MAO) and phosphating to improve the corrosion resistance. The reaction mechanism is investigated and proposed. The coating shows a relatively small surface roughness (Ra = 0.5 μm) and a high Vickers hardness (1200 HV). The corrosion resistance is evaluated by the salt spraying test and Tafel polarization and a lifetime of up to 1800 h and a passivation potential of above 10 V are observed.