Microstructure and Corrosion Resistance of Plasma Electrolytic Oxidized Recycled Mg Alloy

The wide application of Mg is hindered by its low corrosion resistance, especially for recycled Mg. In this work, a novel plasma electrolytic oxidation (PEO) process was conducted on a recycled Mg alloy with a high content of Al (similar to 2.3 wt%), which results in a polycrystalline PEO coating. The PEO coating displays a three-layered structure with a uniform elemental distribution. Unlike the outer layer decorated by channels of micrometre scales, the middle layer mainly contains submicron-sized pores associated with plasma discharges, whereas the fine pores originated from oxygen evolution were detected in the inner layer. The electrochemical measurements, hydrogen evolution tests and salt spray tests were conducted, indicating the superior corrosion resistance of PEO-coated recycled Mg alloy. Hence, the purposed PEO method could dramatically enhance the corrosion resistance of recycled Mg, which may broaden its application in the future.