Effect of oxygen flow on compactness of micro-arc oxidation coatings on LY12 Al alloy

Abstract

Compact and uniform coatings were fabricated on LY12 aluminum alloy surface by adjusting process parameters and oxygen flow after micro-arc oxidation (MAO) treatment. The thickness, morphology, phase compositions and corrosion resistance were examined by SEM, XRD and electrochemical test system. The mechanism of MAO with oxygen was discussed, and the effect of oxygen flow on the coating compactness was analyzed. The results indicate that with the increase of time, voltage and concentration of electrolyte, the coating thickness changes regularly. The effect of oxygen on sintering can promote the growth of compact coatings, and the thickness of compact coatings first increases and then decreases with O2 rising. Under the conditions of 105g/L KF, 85g/L KOH, 12g/L NaAlO2, 110V for the voltage, 15min for treatment time and 0.010L/s for oxygen flow, a 30μm-thick compact coating can be formed on LY12 aluminum alloy. The corrosion potential of the coating increases to -0.11V, and the current density reduces to 2.1×10-6A/cm2, which is reduced by two orders of magnitude compared with the matrix and the corrosion resistance of the LY12 aluminum alloy significantly improves.

Keywords

• aluminum alloy
• micro-arc oxidation
• oxygen flow
• compact coating
• corrosion resistance