Effects of current output modes on the growth kinetics and corrosion resistance of micro-arc oxidation coatings on magnesium alloy

Micro-arc oxidation (MAO) coatings were prepared on the AZ31 Mg alloy under the constant/gradient current control modes. The effects of current output modes on the growth rate, energy consumption, microstructure, and corrosion resistance of MAO coatings were studied. The results shows that the current step-down mode (G852) exhibited a lower unit energy consumption than the constant current mode (C5) and the current step-up mode (G258), even though the same average current density current was used during MAO process. Meanwhile, the G852 is conducive to a thick and dense coating, resulting in a better corrosion resistance. The method of energy saving preparation of corrosion resistant MAO coating by adjusting the current mode is of great significance for practical production.