Synthesis and corrosion of functionally gradient TiO2 and hydroxyapatite coatings on Ti–6Al–4V

TiO2 coating offers excellent corrosion resistance and the bone mineral hydroxyapatite (HA) offers very good biocompatibility. A suitable combination of these coatings is expected to produce good corrosion resistance as well as biocompatibility of an implant. Functionally graded coatings containing TiO2 and HA were produced on Ti–6Al–4V. Three sets of coatings were produced. The bare alloy is heated for 2 h at 800 °C to get TiO2 layer to get the first coating. The next coating consists of two layers, namely, (a) TiO2 produced by heat-treatment and (b) a second layer containing 50% TiO2 and 50% HA. The third sample contains three layers, namely, (a) TiO2 produced by heat-treatment as the first layer, followed by (b) a layer containing 50% TiO2 and 50% HA and (c) third layer of HA electrochemically deposited above the second layer. These three samples were subjected to corrosion tests in Simulated Body Fluid (SBF). It was found that coating 1 containing the oxide alone had the highest corrosion resistance followed by coatings 2 and 3. Coating 2 provides corrosion resistance and will show better implant-bone bonding.