The effect of simulated inflammatory conditions and Fenton chemistry on the electrochemistry of CoCrMo alloy.

Inflamed conditions may develop in total joint replacement applications and may impact on the corrosion of metallic biomaterials like CoCrMo alloy. The influence of simulated inflammatory (SI) conditions on the corrosion behavior of CoCrMo alloy was investigated. A range of SI solutions, based on phosphate buffered saline with H2 O2 , HCl, and Fe3+ additions, were investigated. Open circuit potential (OCP), corrosion currents and impedance of the oxide film surface were all significantly (p < 0.05) affected by increases in H2 O2 concentration and decrease of pH. OCP (vs. Ag/AgCl) increased from -0.250 V in PBS solution to 0.355 V and 0.650 V in 30 mM H2 O2 at pH 7.4 and pH 1 PBS solution. Iron ions (0.1 mM) in PBS solutions with 10 mM H2 O2 (Fenton chemistry) increased OCP to 0.6 V. Icorr increased from 0.2 µA/cm2 to 14 µA/cm2 in SI conditions. Electrochemical impedance spectroscopy showed decreased in oxide resistance (Rox , p < 0.05) while capacitance (CPE) increased (p < 0.05) in SI solutions, pH 7.4 (Rox  = 5 × 103 Ω cm2 , CPE = 55 µF/cm2 ) as well as in Fenton reagent solution (Rox  = 3.2 × 104 Ω cm2 , CPE = 45 µF/cm2 ) compared to PBS only (Rox  = 5 × 105 Ω cm2 , CPE = 31 µF/cm2 ). These results indicate the corrosion susceptibility of CoCrMo alloy can be significantly increased by SI solutions, increasing the oxidizing power and decreasing the passivity of the oxide film. Cell-released chemicals such as H2 O2 and acid are able to facilitate the corrosion of CoCrMo alloy and demonstrate part of the mechanism of inflammatory cell induced corrosion.