Corrosion study of surface-modified vanadium free titanium alloys

Abstract

The present work is part of an investigation aimed to improve the corrosion resistance of three vanadium-freetitaniumalloys of biomedical interest, Ti–6Al–7Nb, Ti–13Nb–13Zr and Ti–15Zr–4Nb, by growing on their surfaces an oxide protective layer. For this goal, different samples were oxidized in air at 750 °C for times ranging from 6 to 48 h. Thickness, morphology and composition of the oxide scales for different oxidation times were investigated by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). After equal oxidation time, the Ti–6Al–7Nb alloy exhibited a thinner, more compact and dense oxide layer than the TiNbZr alloys, indicating a slower oxidation rate. Several oxidation times were used in order to obtain oxide scales with similar properties for the three alloys. Different electrochemical techniques were then applied to evaluate the corrosion behavior of the different samples. The oxidized Ti–6Al–7Nb alloy showed the lowest corrosion current densities as well as the best pitting corrosion behavior, and is thereby considered as the best of these materials for biomedical applications.