Erosion and corrosion resistance of plasma electrolytic oxidized 6082 aluminum alloy surface at low and high temperatures

Abstract

This paper embodies the findings of a study on improving the surface tribology of Al alloy 6082-T6 through plasma electrolytic oxidation (PEO) process. The surface macro/microstructure and composition were investigated. Electrochemical measurements were performed at temperatures of 20 and 80°C using an inductively coupled plasma and open circuit potential tests after immersion in 3.5%NaCl solution. The erosion tests were performed with water carrying sand particles at different sand loadings (200 and 1000mg/l) and temperatures (20 and 80°C). After erosion experiments, the weight loss measurements were recorded, and the worn surfaces were assessed through SEM study and profilometry analysis. The micro-hardness of the coated layer and the substrate were measured before and after the erosion test. The formed PEO layer of 40μm thick was almost sound, uniform, well adhered to the substrate and consisted mainly of alumina phases (α-Al2O3, γ-Al2O3). The relative proportions of α-Al2O3 to γ-Al2O3 were 31: 79%. The PEO coating shows much better corrosion and erosion resistance and less surface damage compared to the aluminum substrate, especially at elevated temperature and high sand loading. The PEO hardness increases as the distance from the substrate increases until near the middle of the coating.