Oxide film Development on a Titanium Alloy Surface Exposed to a Physiological Solution

Titanium and its alloys are widely used as components of human implants, due to their biocompatibility, osteointegration, mechanical properties and corrosion resistance. However, these biomaterials can degrade in time due to corrosion and wear in vivo. The high chloride and oxygen content in the human body fluids makes such environment highly aggressive for metal alloys. The passive surface oxide film that forms on the Ti alloys surface when it becomes in contact with the body fluids protects the metal from further corrosion. Standardized ASTM electrochemical methods used to assess the corrosion resistance have not been very successful to measure accurately corrosion rates of these alloys. In this research, changes in the open circuit times on their effect on the corrosion potential (Ecorr), corrosion current density (icorr), and pitting potential (Epit) are investigated to examine the kinetics during the development of the oxide film at the surface. A metallurgical characterization of a Ti alloy used for hip implant was first conducted. A series of open circuit potential measurements and potentiodynamic electrochemical tests in a phosphate buffered saline physiological solution were ran at room temperature, combined with electrochemical impedance spectroscopy (EIS) to gain a better understanding of the oxide film development and stability.