Influence of microarc oxidation coating microstructure on the corrosion resistance of Al-La alloy in natural seawater environment

• MAO coating have significantly improved the corrosion resistance of Al-10La alloy. • The electrolyte's WC concentration affected the MAO coating's micromorphology • A thick layer with optimal densification and few defects was obtained at 4 g/L WC • Changes in WC concentration alter coating densification, affecting its corrosion resistance. Microarc Oxidation (MAO) coatings on Al-10wt.%La alloy were synthesized by incorporating varying concentrations of tungsten carbide (WC) into the electrolyte. The micromorphology, elemental distribution, three-dimensional morphology, physical phase composition, and corrosion resistance of the resulting MAO coatings were systematically analyzed and characterized. Our findings indicate that the surface micropores, pore diameter, and roughness of the MAO coatings exhibited a biphasic response to the WC concentration, with a decrease followed by an increase as the WC concentration increased. Concurrently, the coating thickness initially increased and then decreased with increasing WC concentration. The MAO coatings significantly enhanced the corrosion resistance of the Al-10La alloy compared to the uncoated substrate. The variation in WC concentration altered the densification of the coatings, which in turn influenced their corrosion resistance. Notably, at a WC concentration of 4 g/L, the MAO coatings demonstrated optimal corrosion resistance.