Effects of electrolytic concentration on properties of micro-arc film on Ti6Al4V alloy

To study the effect of electrolytic concentration, bioactive ceramic films containing Ca and P on the surface of the Ti6Al4V alloy were prepared by micro-arc oxidation (MAO) in aqueous solutions of different concentrations. Composition, micro-morphology, wettability of the films and their corrosion behavior in a Hank's SBF were studied. Our experimental results show that the film is mainly composed of anatase, rutile and amorphous phases. With an increase in electrolytic concentration, the ratio of rutile in films enlarge and small amounts of calcium phosphate (Ca3(PO4)2) and hydroxyapatite (HA) appear. The number of micropores in films increases but their dimensions decrease and their porosities increase slightly. As the surface roughness of MAO film increases with concentration, the wettablility of the oxide film improves continually, while micro-hardness increases at first and then decreases. MAO treatment clearly improves the corrosion resistance of substrates in a Hank's SBF.