日本金属学会誌

J. Japan Inst. Metals, Vol. 59, No. 10 (1995),
pp. 1061-1069

Effect of Mo and Pd on Corrosion Resistance of V-free Titanium Alloysfor Medical Implants

Yoshimitsu Okazaki1, Kenji Kyo2,Yoshimasa Ito3 and Tetsuya Tateishi1

1Mechanical Engineering Laboratory, Agency of Industrial Science and Technology, Ministry of International Trade and Industry, Tsukuba, Ibaraki
2Nippon Institute of Technology, Miyashiro, Saitama

3Technical Development Group, Kobe Steel, Ltd., Kobe

Abstract:

The corrosion resistances of Ti-15%Zr-4%Nb-4%Ta-0.2%Pd-0.2%O-0.05%N and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd-0.2%O alloys were compared with pure Ti grade 2, Ti-6%Al-4%V ELI (Extra low interstitial), Ti-6%Al-2%Nb-1%Ta and β type Ti-15%Mo-5%Zr-3%Al alloys for medical implants by anodic polarization and immersion tests at 310 K in various pseudo saline solutions.
The change in current density was small up to passivity zones in 1% lactic acid, PBS(-), calf serum and eagle's MEM+bovine serum solutions except 5%HCl. The current density change of Ti-15%Zr-4%Nb-4%Ta-0.2%Pd-0.2%O-0.05%N alloy was lowest among the whole Ti alloys. Current density at higher voltage region more than 2 volt tend to be higher in the following relation; Ti-6%Al-4%V ELI>Pure Ti grade 2>Ti-6%Al-2%Nb-1%Ta>Ti-15%Sn-4%Nb-2%Ta-0.2%Pd-0.2%O>Ti-15%Zr-4%Nb-4%Ta-0.2%Pd-0.2%O-0.05%N alloy in α+β type alloys. Otherwise the passive current density of the β type Ti-15%Mo-5%Zr-3%Al alloy was higher than that of α+β type alloys. Passive films formed on Ti-15%Mo-5%Zr-3%Al alloy in the calf serum consisted mainly of TiO2, ZrO2, Al2O3 and Mo as demonstrated by X-ray photoelectron spectroscopy (XPS).

The rate of Ti ion released from Ti alloys in a deaerated 5%HCl solution decreased with increasing Zr, Nb, Ta, and Pd contents. Especially, the rate of Ti ion released from Ti-15%Zr-4%Nb-(2{~}4%)Ta-Pd alloys containing Pd in the range from 0 to 0.2% decreased remarkably compared to 0.2 to 0.5%Pd. The passive films formed on the Ti-Zr-Nb-Ta-Pd and Ti-Sn-Nb-Ta-Pd alloys containing 0.2%Pd in the immersion test consist mainly of TiO2, ZrO2, SnO2, Sn, Nb2O5, Ta2O5 and Pd or PdO. The rate of released Ti increased by the following relation; Ti-15%Sn-4%Nb-2%Ta-0.2%Pd-0.2%O≥qqTi-6%Al-2%Nb-1%Ta≥qqTi-6%Al-4%V ELI≥qqPure Ti grade 2>Ti-15%Zr-4%Nb-4%Ta-0.2%Pd-0.2%O-0.05%N≥qqβ type Ti-15%Mo-5%Zr-3%Al alloy.


(Received February 13, 1995)

Keywords:

titanium alloy, medical implant, corrosion resistance, pseudo saline solution, anodic polarization curve, immersion test, X-ray photoelectron spectroscopy, effect of alloying element


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