Comparison of in vitro corrosion products on CoCrMo generated via oscillatory electric fields before and after removal of proteinaceous layer

Although surgical success and patient mobility have greatly benefited from the increased modularity found in modern hip prosthetics, significant corrosion complications remain. Whereas the majority of biometallic corrosion research focuses on fretting and/or crevice corrosion, this manuscript investigates a largely unexplored biometallic corrosion phenomenon, induced via low magnitude, high frequency electric potential oscillations without mechanical wear. A detailed comparative study is provided for each test condition before and after the removal of the organic deposition film. Samples shielded from electrical oscillation showed no corrosion activity, whereas samples subjected to electrical activity showed significant corrosion activity. Consistent with in vivo corrosion analysis, the protruding growths contained: Cr₂O₃, CoO, CoOH, and compounds containing Ca, P, and Cr (VI). In addition to protruding growths, select electrical activity is identified as initiating significant pitting between the organic layer and the metallic surface. This manuscript highlights the following key findings: 1. The presence of low magnitude, high frequency electrical oscillation is sufficient to generate corrosion products, chemically consistent with those recovered in vivo. 2. Variation in electrical signal form significantly alters the initial organic deposition and predominate corrosion mode. 3. The formation of surface pitting, under electrical excitation, was preceded by substantial accumulation of P and Ca in the organic deposition layer.