Synthesis and corrosion of functionally gradient TiO<inf>2</inf> 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. © 2007 Elsevier B.V. All rights reserved.