Influence of titania sol in the electrolyte on characteristics of the microarc oxidation coating formed on 2A70 aluminum alloy

The effects of a titania sol in an alkaline phosphate electrolyte on the thickness, surface morphology, composition and abrasive resistance of a microarc oxidation (MAO) coating on 2A70 aluminum alloy were investigated. The voltage–time curve was used to characterize MAO process. The coating thickness increased with increasing the concentration of the titania sol in the electrolyte, accompanied with the increase in surface nonuniformity and size of micropores in the coating surface. The MAO coating formed in the titania sol free electrolyte was mainly composed of γ-Al2O3 and a little α-Al2O3. Titanium in the form of Al2TiO5, Ti2O3 and TiO was detected in the MAO coatings obtained in the electrolyte containing titania sol, and the content increases with increasing the concentration of titania sol. The MAO coating formed in the electrolyte containing 6.0 vol.% titania sol exhibited the highest microhardness and abrasion resistance.