Sol–gel derived hydroxyapatite coating on titanium implants: Optimization of sol–gel process and engineering the interface

Sol–gel derived hydroxyapatite coatings on metallic implants are important to promote their osseointegration and biocompatibility. However, such coatings generally suffer from drawbacks that limit implant longevity. In this study, the sol gel process to prepare hydroxyapatite was optimized and used to deposit a hydroxyapatite layer on Ti6Al4V. Samples were pretreated by thermal oxidation, sol–gel coating, and anodization to produce titanium dioxide interlayers with various structures. The results of structural and thermal analysis have determined the optimal preparation parameters to produce monophasic and crystalline hydroxyapatite. The introduction of titanium dioxide intermediate layers produced crack-free hydroxyapatite films and promoted the adherence and integrity of the coating, where the adhesive strength was remarkably improved. Furthermore, potentiodynamic polarization tests in simulated body fluid revealed low corrosion rates and high protection property of the hydroxyapatite/titania coated samples, making these structures promising for the coatings of bone replacements.