FRETTING CORROSION IN ORTHOPAEDIC IMPLANT ALLOYS

Abstract

This chapter presents the studies of fretting corrosion in orthopaedic alloys as a function of material, the number of cycles and the solution in which the fretting occurred to further characterize the mechanisms and tendencies of this phenomenon. Weight loss appears to be of major significance in the early stages of fretting but reaches a steady state where additional weight loss is negligible. Less additional debris was created during the steady state because there was a build-up of debris which forms an intermediate zone. This build-up pushes the two surfaces apart. The stress transmitted across the two surfaces was lowered because of this increase in area with number of cycles. The corrosion process was hindered by anodic polarization. In this experiment, the debris formed becomes a product of corrosion and/or is embedded into one of the surfaces. These embedded particles often cause microcracks in the surface as they were pushed in. These cracks create crevices which can lend themselves to more deleterious forms of corrosion. The bands of the colors observed at the edge of fretted areas represent different stages of oxidation. It was observed that when the metals were tested in the saline and albumin solution, there appeared a slippery film which was most likely the precipitation of the albumin onto the metal surface.