Formation of multi-functional TiO2 surfaces on AA2024 alloy using plasma electrolytic oxidation

Abstract

Plasma electrolytic oxidation (PEO) was applied to functionalise the surface of AA2024 alloy. A potassium titanium-oxide oxalate dihydrate based aqueous electrolyte was used, which allowed the direct formation of a TiO2 surface layer on the aluminium alloy substrate. The effect of PEO treatment time and the additional presence of anatase particles in the electrolyte solution on the surface layer and its properties (corrosion, wear and photocatalytic activity) were investigated. It was found that the coating thickness and surface morphology are strongly dependent on the PEO processing time. However, the phase composition is not much affected by the treatment time and the main coating phase is rutile with a smaller amount of anatase. Adding additional anatase in the form of particles increases the amount of anatase in the coatings. The additional particle addition has only minor effect on the corrosion resistance, but reduces the wear resistance remarkably. Interestingly, the addition of anatase particles and the PEO treatment time are not effective in increasing the photocatalytic activities of the samples.