Comparison of Key Properties of Ag-TiO₂ and Hydroxyapatite-Ag-TiO₂ Coatings on NiTi SMA

To functionalize the NiTi alloy, multifunctional innovative nanocoatings of Ag-TiO₂ and Ag-TiO₂ doped with hydroxyapatite were engineered on its surface. The coatings were thoroughly characterized, focusing on surface topography and key functional properties, including adhesion, surface wettability, biocompatibility, antibacterial activity, and corrosion resistance. The electrochemical corrosion kinetics in a simulated body fluid and the mechanisms were analyzed. The coatings exhibited hydrophilic properties and were biocompatible with fibroblast and osteoblast cells while also demonstrating antibacterial activity against E. coli and S. epidermidis. The coatings adhered strongly to the NiTi substrate, with superior adhesion observed in the hydroxyapatite-doped layers. Conversely, the Ag-TiO₂ layers showed enhanced corrosion resistance.