生体用Ti合金の生体内模擬環境下における耐食性

Abstract

The effect of alloying elements on the corrosion resistance of titanium alloys for medical implants was investigated by immersion tests in an aerated 5%HCl solution for 864 ks at 310 K and anodic polarization measurements in a phosphate buffer solution containing chloride (PBS(−)). The concentration of released Ti in the 5%HCl solution decreased with increasing Zr, Ta, and Pd contents in the range from 10 to 15, 2 to 4 and 0 to 0.2%, respectively, although Nb and Sn had an adverse effect in the range from 4 to 8 and 10 to 15 mass%, respectively. However, Zr and Sn alloying over 15% in Ti-(15∼20%)Zr-4%Nb-2%Ta-0.2%Pd and Ti-(15∼20%)Sn-4%Nb-2%Ta-0.2%Pd, respectively, showed very little difference in the concentration of released Ti, compared with those less than 15%. Especially combined alloying of 0.2%Pd and (2∼4%)Ta remarkably decreased the concentration of released Ti in the 5%HCl solution. N addition into the Pd-free Ti-10%Zr-4%Nb-2%Ta-0.1%O alloy increased the concentration of released Ti. The critical currrent density for passivation (Ic) of the titanium alloys in the PBS(−) decreased with increasing Zr, Nb, Ta and Pd contents. The Ic values in the PBS(−) decreased as those in the 5%HCl solution decreased. The concentration of released Ti from the Ti-15%Zr-4%Nb-(2∼4%)Ta-0.2%Pd and Ti-15%Sn-4%Nb-(2∼4%)Ta-0.2%Pd alloys in the 5%HCl solution were less than that from the Ti-6%Al-4%V ELI alloy by a factor of 52∼520.