The effect of simulated inflammatory conditions and pH on fretting corrosion of CoCrMo alloy surfaces

Inflammation may develop due to the implantation of orthopedic devices and inflammatory cell-based chemical species may affect the fretting corrosion behavior of CoCrMo alloy. The effect of simulated inflammatory (SI) conditions and acid on the fretting corrosion behavior of CoCrMo was studied. SI conditions included phosphate buffered saline (PBS) with H2O2 and PBS with Fenton reaction (Fe3+, H2O2). Fretting corrosion behavior of CoCrMo alloy was significantly affected by both the Fenton reaction-based solution chemistry and potential. The Fenton reaction increased the oxidizing power of the solution and led to a significant rise in open circuit potential (OCP) during fretting corrosion compared to PBS and pH 3 solutions (p < 0.05). SI conditions also altered the oxide film characteristics, altering both the fretting corrosion response of CoCrMo alloy (smaller fretting currents by about 50%) and the frictional behavior compared to the PBS case. Fretting current density in Fenton reaction conditions was significantly smaller compared to PBS conditions at all potentials, indicating the oxide film was less protective due to the presence of Fenton reactions. A significantly higher coefficient of friction was observed in Fenton reaction solutions at -0.4 V (0.5) and -0.6 V (0.55) compared to all other conditions. This appears to be related to the oxide formation potential (-0.4 V) and the effects of solution chemistry on sliding mechanics. Passivation of oxide film was the strongest in pH 3 condition, where baseline current density was the lowest at 0.6 V compared to that of other solutions (p < 0.05).