Electrochemical corrosion behavior of a Ti-35Nb alloy for medical prostheses

Since the 1980s, the titanium alloys show attractive properties tor biomedical applications where the most important factors are, firstly, biocompatibility, corrosion and mechanical resistances, low modulus of elasticity, very good strength to weight ratio, reasonable formability and osseointegration. The aim of this Study was to investigate the effects of two different heat treatments; furnace cooling and water quenching, on the general electrochemical corrosion resistance of Ti-35 wt%Nb alloy samples immersed in a 0.9% NaCl (0.15 mol L-1) solution at 25 degrees C and neutral pH range. The samples were obtained using a non-consumable tungsten electrode furnace with a water-cooled copper hearth under argon atmosphere. The microstructural pattern was examined by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). In order to evaluate the electrochemical corrosion behavior of such Ti-Nb alloy samples, corrosion tests were performed by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. Analyses of an equivalent circuit have also been used to provide quantitative Support for the discussions and understanding of the corrosion behavior. It was found that water quenching provides a microstructural pattern consisting of' an alpha-martensite acicular phase which decreases the material electrochemical performance due to the stress-induced martensitic transformation. (c) 2008 Elsevier Ltd. All rights reserved.