Micro-abrasion–corrosion of a CoCrMo alloy in simulated artificial hip joint environments

Abstract

This study aims to investigate the synergistic effects of corrosion and wear of artificial human joints made from a surgical grade cast F-75 cobalt–chromium–molybdenum (CoCrMo) alloy. Both electrochemical and gravimetric measurements have been used to determine the performance of CoCrMo samples in static environments and under predominantly three-body abrasive wear conditions using the micro-abrasion test method. Electrochemical measurements are presented from embedded corrosion cells within a micro-abrasion rig. Micro-abrasion–corrosion has been studied using an aggressive abrasive slurry (SiC/Ringer's) to identify depassivation and repassivation processes. These initial conditions are an attempt to simulate worst-case scenarios where wear, cement or bone debris are entrained into the contact. The in situ wear-corrosion measurements have been used to identify the implications of wear and corrosion on both the implant and tentative implications for the patient over the long term. Results show strong synergistic effects occur ranging from negative to positive (i.e. beneficial to accelerated surface removal rates). The synergistic levels appear to be dependent on the integrity of the passive films and the repassivation kinetics. Corrosion potentials are presented which corroborate depassivation within the scar.