ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY STUDY OF THE PASSIVE OXIDE FILM ON TITANIUM FOR IMPLANT APPLICATION

The surface oxide film on titanium and its long-term stability in biol ogical environments play a decisive role for the biocompatibility of t itanium implants. In this study, the passive oxide film formed on tita nium and its natural growth in a phosphate buffered solution with and without an H2O2 addition have been investigated by electrochemical imp edance spectroscopy (EIS) measurements over a period of several weeks. In the absence of H2O2, the impedance response indicated a stable thi n oxide film on titanium. However, the introduction of H2O2 into the s olution resulted in significant changes in the EIS-spectra, which vari ed with exposure time. The interpretation of results is based upon a t wo-layer model of the oxide film, consisting of a thin barrier-type in ner layer and a porous outer layer. The H2O2 addition in the solution led to a significant decrease in corrosion resistance of titanium and also to a thickening of the porous outer layer. The observations may p rovide an explanation of the unexpected in vivo titanium oxide growth and ion incorporation into titanium implant oxide surfaces.