LAUSR

Abstract Colored coatings with thermally activated red mud (RM) as an electrolyte additive were applied to 5005 aluminum alloy using the plasma-electrolytic-oxidation (PEO) technique. Effects of the RM on the PEO coating composition, structure, and properties were investigated. The pure PEO coating was white and consisted of γ-Al2O3 and α-Al2O3. The RM PEO coatings were colored, and consisted of α-Al2O3 and γ-Al2O3, plus CaTiO3, CaCO3, SiO2, Fe2O3, and mCaO·nAl2O3·xFe2O3·ySiO2, which were formed at high temperatures. Surface porosities and hardnesses for most of the RM PEO coatings were lower, but their thicknesses and coating/substrate bonding strengths were higher (and increased with increasing coating thickness), and their structures were denser than those of the pure PEO coating. After 30 min erosive wear, mass loss and wear scars for most of the RM PEO coatings were lower than those of the pure PEO coating. This indicates good wear resistance. Electrochemical corrosion tests showed that the RM PEO coating corrosion resistances were better than that of the pure PEO coating, especially for heat treatment at 300 °C.