In vitro bioactivity and corrosion resistance enhancement of Ti-6Al-4V by highly ordered TiO2 nanotube arrays

In the present study, the structural features, corrosion behavior, and in vitro bioactivity of TiO2 nanotubular arrays coated on Ti-6Al-4V (Ti64) alloy were investigated. For this reason, Ti64 plates were anodized in an ammonium fluoride electrolyte dissolved in a 90:10 ethylene glycol and water solvent mixture at room temperature under a constant potential of 60 V for 1 h. Subsequently, the anodized specimens were annealed in an argon gas furnace at 500 and 700 A degrees C for 1.5 h with a heating and cooling rate of 5 A degrees C min(-1). From XRD analysis and Raman spectroscopy, a highly crystalline anatase phase with tetragonal symmetry was formed from the thermally induced crystallization at 500 A degrees C. Besides, the Ti 2p(3/2) and Ti 2p(1/2) binding energies showed the presence of the Ti4+ oxidation state. According to the in vitro bioassay, the modified surface proved its outstanding capability in enhancing the bioactivity, where a thick layer of bone-like apatite was formed on the annealed TiO2 nanotube surface. In addition, the corrosion measurements indicated that the corrosion protection efficiency increased remarkably and reached 87% after annealing at 500 A degrees C.