Formation of self-repairing anodized film on ACM522 magnesium alloy by plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) on a die-casting ACM522 Mg alloy was conducted in aqueous silicate and phosphate solutions. The corrosion behavior of the anodized ACM522 Mg alloy was investigated in detail. During the investigation, the self-repairing behavior of the anodized films was evaluated by a salt spray test for 168 h, and the mechanism of this self-repairing was discussed in terms of thermodynamic equilibrium constants. Furthermore, the effects of additives to the phosphate solution on the self-repairing behavior were examined, and the addition of Na2B4O7 was found to effectively reduce cracks on a self-repaired film.