The influence of proteins on the fretting-corrosion behaviour of a Ti6Al4V alloy

The effects of collagen and albumin on the fretting-corrosion behaviour of a Ti6Al4V alloy contacting an Al₂O₃ counter-piece was investigated in pH buffered saline solutions at 37 °C using a tribo-electrochemical apparatus. Phosphate ion and hydroxyethyl-piperazinyl-ethanesulfonic acid (HEPES) were used as the pH buffer agents. Tests were conducted under two applied electrochemical potentials and two loads. Potentiodynamic polarisation curves were measured to assess the effect of proteins and pH buffer agents on the corrosion behaviour. Surfaces were characterised by XPS analysis, secondary electron spectroscopy and laser profilometry. Fretting wear of the Ti6Al4V alloy increased with increasing applied potential and load but was not significantly affected by the presence of collagen or albumin. Only a small lubricant effect of collagen could be observed at cathodic potentials. In phosphate buffer saline (PBS) solutions, those proteins were found to act as cathodic inhibitor by shifting the corrosion potential and the cathodic current towards more cathodic values. Phosphate ions were found to be incorporated on the Ti6Al4V alloy and to cause sedimentation of wear particles around the wear trace. In HEPES solutions wear particles were dispersed away from the wear trace.