Detrimental Effect of LPSO Phase on the Corrosion Resistance of Micro-Arc Oxidation Coatings in Mg Alloys

The role of the long-period stacking ordered (LPSO) phase on the microstructure and corrosion properties of micro-arc oxidation (MAO) ceramic coatings was systematically investigated in this study. Optical microscopy and scanning electron microscopy (SEM) were employed to characterize the MAO coatings, while their corrosion behavior was evaluated through electrochemical measurements and immersion tests in a 3.5 wt.% NaCl solution. The results reveal that the sample containing the LPSO phase exhibited an increased coating thickness. However, the coating formed on the LPSO-containing Mg alloy presented a highly porous morphology with numerous large micropores. This defective microstructure compromised the protective barrier function of the ceramic layer, ultimately resulting in inferior corrosion resistance compared to coatings on its LPSO-free counterparts.