Biotribocorrosion: Some electrochemical observations from an instrumented hip joint simulator

36 mm Metal-on-Metal heads and cups were tested in a hip joint simulator instrumented with a 3-electrode electrochemical cell. This facilitated in situ monitoring of the tribological depassivation of the bearing surface. Subsurface analysis of the different regions of the femoral head was analysed using transmission electron microscopy. It was found that tribological depassivation increased the rate of corrosion, but subsequently decreased at around 450,000 cycles. Observations of the subsurface microstructure revealed the formation of nano-crystallites and the presence of micro-scale subsurface cracks.