In vitro Corrosion Study of Two Implant Materials Using Electrochemical ImpedanceSpectroscopy and Potentiodynamic Polarization

摘要

In vitro corrosion evaluations of commercially pure titanium (CP-Ti) and Ti-6Al-4V samples with different surface treatments were conducted using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The different surface treatments tested were as-polished, nitric acid passivated (ASTM F86), and anodized. The test solution consisted of oxygenated 0.9 normal NaCl buffered to a pH of 7.3 at 37 deg C. The corrosion properties were shown to be similar for the two metals in the polished and passivated condition. The CP-Ti was found to be more corrosion resistant than the Ti-6Al-4V in the anodized condition. For both metals, the anodized condition was much more corrosion resistant than the passivated condition which was more corrosion resistant than the as-polished condition. The oxide layer on both metals in the as-polished and passivated conditions as well as on the CP-Ti in the anodized condition was composed of non-porous TiO2. The protection provided by this layer was found to be related to its thickness. The oxide on the anodized Ti-6Al-4V was composed of a porous layer of hydrated TiO3 on top of a nonporous layer of TiO2. Although this layer was thicker than that on the anodized CP-Ti, it did not provide as much protection against corrosion.