Abstract In this study, hydroxyapatite (HA) was synthesized via the sol–gel method and characterized to ensure phase purity and nanoparticle formation. Titanium machining chips were recycled and transformed into nanopowder using planetary ball milling to enhance material sustainability. Composite coatings of HA–TiO 2 were subsequently deposited onto Ti6Al4V alloy substrates through electrophoretic deposition (EPD) at a constant voltage of 45 V for 90 s, with HA contents of 10, 20, 30, and 40 wt%. After drying at ambient conditions, the coated samples were vacuum-sintered at 1100 °C for 4 h. Microstructural and phase analyses conducted by SEM and XRD revealed the formation of dense, homogeneous coatings composed of Ti, HA, and oxide phases. Based on EIS and polarization analyses in simulated body fluid, the corrosion resistance of all coated samples was considerably superior to that of the untreated Ti6Al4V alloy. Among them, the coating containing 30 wt% HA demonstrated the highest corrosion resistance, which was attributed to its uniform and stable phase distribution. Overall, this study presents a cost-effective and sustainable strategy to recycle Ti6Al4V machining chips for developing biocompatible coatings with superior corrosion protection for metallic implant applications.
Kavanlouei et al. (2026) studied this question.