Time-Dependent Electrochemical Behaviour and Surface Response of Ti6Al7Nb and Ti6Al4V Alloys in Albumin-Containing PBS

The electrochemical and surface behaviour of implant-grade commercially pure titanium (cp-Ti), Ti6Al7Nb, and Ti6Al4V clinically used alloys was investigated in phosphate-buffered saline (PBS), with and without albumin, at 37 °C using electrochemical techniques and SEM/EDS analysis. In PBS, the corrosion resistance followed the order Ti6Al4V < Ti6Al7Nb < cp-Ti, with cp-Ti serving as the benchmark reference material. The addition of albumin improved the corrosion resistance of all materials under the investigated static in vitro conditions, with the most pronounced effect observed for Ti6Al4V. Over time, the oxide layer stabilised and the differences between the materials decreased, with Ti6Al4V approaching the behaviour of more stable systems. Surface analysis revealed a comparatively more uniform (but not fully homogeneous) protein distribution on Ti6Al7Nb, whereas Ti6Al4V exhibited localised adsorption associated with greater surface heterogeneity. Protein adsorption acts as a stabilising interfacial factor, contributing to improved protective properties under static conditions. These findings highlight the key role of surface heterogeneity in governing protein adsorption and electrochemical behaviour of titanium alloys under biologically relevant conditions.