Effect of Lanthanum Oxide on Microstructure and Corrosion Properties of 6061 Aluminum Alloy Micro-arc Oxide Film

In order to improve the overall performance of 6061 aluminum alloy, this paper adds La₂O₃ to the electrolyte for micro-arc oxidation and studies the effect of lanthanum oxide concentration on the structure and performance of the film. The results show that the basic phases of the films are Al, α-Al₂O₃, γ-Al₂O₃, SiO₂ and mullite. The micro-arc oxidized film layer is a porous structure, and the corrosive medium and the substrate form a double electrical layer structure, which causes corrosion. The addition of La₂O₃ improves the densification of the film layer, and the holes or cracks are reduced, but too much La₂O₃ will accumulate on the surface, causing the porosity to increase. Therefore, with the increase of La₂O₃ concentration, the porosity and roughness of the film layer decrease and then increase, and the thickness hardness and corrosion resistance increase and then decrease. When the dosage of La₂O₃ is 1.0 g/L, the thickness and hardness are the largest, the roughness is the smallest, the corrosion resistance is the best, and the self-corrosion current density is 9.986 × 10^-10 A/cm². When the dosage of La₂O₃ is 1.0 g/L, the overall performance of the micro-arc oxidation film is the best.