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

Abstract

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. I_corr increased from 0.2 µA/cm² to 14 µA/cm² in SI conditions. Electrochemical impedance spectroscopy showed decreased in oxide resistance (R_ox , p < 0.05) while capacitance (CPE) increased (p < 0.05) in SI solutions, pH 7.4 (R_ox  = 5 × 10³ Ω cm² , CPE = 55 µF/cm² ) as well as in Fenton reagent solution (R_ox  = 3.2 × 10⁴ Ω cm² , CPE = 45 µF/cm² ) compared to PBS only (R_ox  = 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. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 209-220, 2018.