Study of the biotribocorrosion behaviour of titanium biomedical alloys in simulated body fluids by electrochemical techniques

The corrosion and wear behaviour of wrought titanium alloys (Ti-Grade 2, Ti6Al4V and Ti6Al4V-ELI) immersed in phosphate buffered solution (PBS) and phosphate buffered solution with bovine serum albumin (PBS+BSA) has been analysed by electrochemical techniques and surface microscopy. The influence of the alloy composition and microstructure on the tribo- electrochemical behaviour was analysed by potentiodynamic studies and potentiostatic tests (applied electrochemical potentials) under sliding conditions. Plastic deformation and third bodies were observed at the end of the tests by optical, confocal and scanning electron microscopy (SEM). Although the degradation mechanism was the same in all the studied alloys, wear debris was found to be material and solution chemistry dependent. α+β phase Ti6Al4V alloy shows lower wear damage than the α phase Ti-Grade 2 alloy. Main effect of chemical composition and microstructure of the alloy was found in the wear accelerated corrosion, which is twice in the case of the Ti-Grade 2. Effect of the repassivation time and passive film growth on the wear behaviour of the Ti6Al4V-ELI was also analysed by carrying out intermittent tests. Wear coefficient increases when rest time between sliding cycles increases due to the growth of the passive films during the pause periods. BSA adsorbs on the metallic surface thus reducing the repassivation kinetics and therefore hindering the effect of pause periods during sliding.