Properties of Micro-Arc Oxidation Coatings on 5052 Al Alloy Sealed by SiO2 Nanoparticles

Micro-arc oxidation (MAO) treatment can effectively improve the wear resistance, corrosion resistance, and mechanical strength of aluminum alloy substrates. Improving the porous structure of MAO film and effectively sealing the pores is a significant research issue. In this study, the MAO treatment of 5052 aluminum alloy was carried out in silicate electrolytes. The MAO films were sealed with different concentrations of SiO2 nanoparticles. The effects of SiO2 nanoparticle content on the MAO films’ microstructure, mechanical properties, and corrosion performance were systematically investigated. When adding SiO2 nanoparticles to electrolytes, the particles were deposited at the micropores of the film, which could effectively seal the porous MAO film and significantly improve its corrosion and wear resistance. The corrosion resistance and wear resistance properties were optimal with 5.0 g/L SiO2 addition. Compared to the unsealed film, the corrosion current density and corrosion rate decreased from 1.24 × 10−9 A/cm2 and 1.47 × 10−5 mm/a to 7.78 × 10−10 A/cm2 and 9.15 × 10−6 mm/a, respectively. Moreover, the average friction coefficient of the sealed film was 0.606, which was ~19.3% lower than that of the substrate and 3.3% lower than for the unsealed film.