A Comparative Electrochemical Assessment of Multifunctional Coatings TiO₂ and TiON for Biomedical Implant Applications

In the realm of implants application, the corrosion resistance phenomenon against the intricate physiological environment within the human body is of utmost importance. Despite, Ti64 alloy exhibiting commendable corrosion resistance along with good biocompatibility, it is vulnerable to get corroded in complex biological environment particularly during long term application. Oxide multifunctional coatings serve as resilient protective barrier against the corrosive environment, thereby making them highly favoured for implant’s coating application. In the present study Titanium oxide $\left(\mathrm{TiO}_{2}\right)$ and Titanium oxynitride (TiON) coatings were successfully developed on Ti64 alloy substrate. Field emission scanning electron microscopy (FESEM) and Energy dispersive spectroscopy (EDS) were utilized to analyse the coating’s morphology and elemental composition. Surface roughness parameters of the coating (Ra and Rq) were determined through atomic force microscopy (AFM). Surface wettability of coating was examined by measuring water contact angle through sessile drop method. The corrosion study was carried out by potentiodynamic polarization test followed by Electrochemical impedance spectroscopy (EIS) in the corrosive media of physiological saline solution. The surface coated with TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and TiON exhibited higher wettability compared to the bare Ti64 alloy surface. Additionally, the wettability of the TiON coating was significantly better than that of the TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> coating. The corrosion test results demonstrates that both $\mathbf{T i O}_{2}$ and TiON coatings exhibited the higher corrosion potential and lower current density values as compared to bare Ti64 substrate. Whereas, TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> coating shows a higher polarization resistance than TiON coating as it forms a strong passivation layer due to its inert characteristics. Conversely, the presence of nitrogen atoms in TiON coating increases its electrical conductivity, leading to a higher corrosion rate. Likewise, EIS results indicated that TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> coating demonstrated better corrosion resistance as compared to the TiON coating.