Effect of Electrical Parameters on Corrosion Resistance of MAO Coating Fabricated on Mg Alloy Under Unipolar Mode
Ceramic coating was obtained by micro-arc oxidation technique on AZ91D Mg alloy under unipolar mode in silicate-aluminate dual electrolyte.The effects of electrical parameters(current density,positive duty cycle,treating time and frequency) on the corrosion resistance of MAO coating fabricated on the Mg alloy were investigated by an orthogonal experiment of four factors with three levels.The results show that the order of affecting corrosion resistance from high to low is as follow: treating time,positive duty cycle,current density and frequency.Good corrosion resistance coating is obtained when the current density is 22 A/dm2,positive duty cycle is 40%,treating time is 12 min and frequency is 500 Hz.Compared with the Mg alloy substrate,the corrosion potential of the coated sample increases by 36.4 mV,and the corrosion current density of the coated sample decreases one order of magnitude.