Effect of indium (In) on corrosion and passivity of a beta-type Ti-Nb alloy in Ringer's solution

Beta-phase Ti-Nb-based alloys are considered as new generation of biomaterials with improved mechanical compatibility for load-bearing implant applications. Small homogeneously dissolved In additions have a positive impact on the elastic properties of beta-type Ti-40Nb. For (Ti-40Nb)-41n the best match between low Young's modulus, high elastic energy and appropriate strength was achieved. In the present study the effect of In addition to Ti-40Nb on the corrosion and passivation behavior in Ringer's solution is assessed by means of potentiodynamic polarization, ICP-OES metal release analysis, XPS and ToFSIMS for passive film characterization. Like Ti-40Nb, (Ti-40Nb)-41n exhibits very low corrosion rates (i(corr) = 0.1-0.2 mu A/cm(2)) and stable anodic passivity (i(pass) = 3-4 mu A/cm(2)). Small In additions do not have a detectable effect on the anodic response of the alloy. For both beta-phase alloys metal release rates are below the quantification limits of ICP-OES. 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 which were formed during OCP exposure or anodic polarization comprise oxidized In species (In2O3, In(OH3)). From the viewpoint of corrosion stability (Ti-40Nb)-41n appears to be suitable for implant applications. 2015 Published by Elsevier B.V.