Corrosion-wear evaluation of a UHMWPE/Co–Cr couple in sliding contact under relatively low contact stress in physiological saline solution

Abstract

Abstract Several tribocorrosion studies have been carried out using metal on metal (MOM) and ceramic on metal (COM) materials combinations in order to understand the behavior of these materials when applied in human joint replacement. However, there are few studies in this area focused on processes of tribocorrosion occurring at the interface between a metal and a polymer. Thus, the aim of this study was to evaluate the tribocorrosion behavior between cobalt chromium and ultra-high molecular weight polyethylene (UHMWPE) under relatively low contact stress. Reciprocating corrosion–wear tests were performed using plates of cobalt-chromium alloy and UHMWPE pins under a load of 1.84 N (giving a contact stress of 39 kPa) in a 0.9% NaCl solution, during 1 h. The tribocorrosion tests were performed at open circuit potential (OCP), during anodic polarization scans and at potentiostatic conditions of −150, −100, 200 and −800 mV vs. SCE. The electrochemical wear rates were estimated using the Faraday equation. The OCP results showed a dramatically decrease of potential during the mechanical contact, while the anodic polarization scans revealed an increase of current during mechanical contact. Finally, potentiostatic tests carried out at −150, −100 and 200 mV vs. SCE displayed an increase of anodic current during mechanical contact, while the tests carried out under −800 mV vs. SCE showed an increase of the cathodic current during mechanical contact. Thus, this set of results provides evidences of tribocorrosion when the mechanical contact was applied to the system, even though the applied stress was relatively low.