Corrosion resistance of implant alloys in pseudo physiological solution and role of alloying elements in passive films

The corrosion resistance of implant alloys was investigated by anodic polarization measurements in a pseudo physiological solution. Role of alloying elements in passive him formed on implant alloys by the anodic polarization was also examined with X-ray photoelectron spectroscopy (XPS). Passivity zones of SUS316L stainless steel:and Co-Cr alloys are narrow, and a rapid increase in the current density is observed from a low potential as compared to Ti alloys. The passive current density of Ti-15%Zr-4%Nb-2%Ta-0.2%Pd alloy (mass%) is very low. Effects of protein and dissolved oxygen with 90%N-2+5%CO2+5%O-2 gas bubbling on anodic polarization curves are not detected. The passive film formed on the Ti-6%Al-4%V extra low interstitial alloy consists mainly of TiO2, Al2O3 and small amounts of V oxide. Passive films on the Ti-15%Zr-4%Nb-2%Ta-0.2%Pd and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd alloys consist of TiO2, ZrO2, SnO2, Nb2O5, Ta2O5 and PdO or Pd. XPS spectra from the Co-Cr alloy and SUS316L stainless steel show peaks of Cr2O3, CoO, Fe oxide, Mo oxide, Ni, Co, Fe, Mo and Cr. As Ni, V and Co are strong cytotoxic elements, it was found that biocompatibility of SUS 316L., Co-Cr, Ti-6%Al-4%V ELI alloys become lesser after a long time use in the living body. The thickness of the passive film on Ti alloys is thinner than that of Co-Cr alloy. Passive film formed on the Ti-15%Zr-4%Nb-2%Ta-0.2%Pd alloy is strong and stable.