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. •P and Fe are introduced into the MAO coating to improve the corrosion resistance.•The reaction mechanism in the newly designed electrolyte is proposed.•A 20 μm thick and compact coating composed of alumina and Fe is obtained.•Extra-long corrosion lifetime (1800h) is obtained by the salt spraying test.•Extra-wide passivation potential (10 V) is revealed by Tafel curves.