Corrosion and passivity of a beta-type Ti–Nb alloys in Ringer’s solution

(Korrosion und Passivität von beta-Ti-Nb Legierungen in Ringerlösung)

Beta-type Ti-Nb-based alloys belong to the promising new generation of biomaterials with improved mechanical compatibility suitable for load-bearing bone implant applications. Small In additions homogeneously dissolved in the beta-phase have a positive impact on their elastic properties. For (Ti-40Nb)-4In the best match between low Young’s modulus, high elastic energy and suitable strength was achieved. However, the corrosion behavior in physiological media determines the biocompatibility and long-term stability of an implant. The effect of In addition to Ti-40Nb on the behavior in Ringer’s solution was assessed by means of potentiodynamic polarization, chemical solution analysis, XPS and ToF-SIMS. Like Ti-40Nb, (Ti-40Nb)-4In exhibits extremely low corrosion rates and very stable anodic passivity. In consequence metal release rates are below the quantification limits. Their strong passivating nature is governed by the formation of thin barrier-type Ti- and Nb-oxide films. Passive films on (Ti-40Nb)-4In surfaces comprise small fractions of oxidized In species (In2O3, In(OH3)).

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