Enhancing corrosion resistance of plasma electrolytic oxidation coatings on AM50 Mg alloy by inhibitor containing Ba(NO3)2 solutions

In order to enhance the long-term corrosion resistance of the plasma electrolytic oxidation (PEO) coating on Mg alloy, an inorganic salt is used in combination with corrosion inhibitors for post-treatment of the coating. In this study, corrosion performance of PEO-coated AM50 Mg was significantly improved by sodium lauryl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS) loaded into the Ba(NO3)2 post-sealing solution. SEM, XPS, XRD, FTIR, and UV-Vis analyses showed that the inhibitors enhanced the deposition of BaO2 on the coating surface. Electrochemical impedance showed that the post-sealing in SDS containing electrolyte enhanced corrosion resistance of the sample by three orders of magnitude. After immersing in 0.5wt% NaCl solution for 768 h, the total impedance value remained at 106 Ω/cm². 40 days of continued salt spray test virtually did not show any obvious region of corrosion, proving the excellent corrosion performance of the coatings after performing post-treatment. The corrosion resistance of the coating was enhanced through the synergistic effect of deposition products and adsorption of inhibitors.