Fretting corrosion with proteins: The role of organic coating on the synergistic mechanisms

Fretting corrosion is one of the most deleterious mechanisms for the degradation of metallic biomaterials, especially in the orthopedic field. This work is dedicated to studying the synergistic effect of proteins and ionic concentration on the wear of 316L stainless steel against a polymer sample under fretting-corrosion conditions. A specialized device produces repeatable fretting corrosion conditions. In order to compare with previous investigations, the relative displacement was chosen to be +/- 40 mu m in a sinusoidal pattern. The duration of each test was 14,400 s. 4 solutions of NaCl were selected in order to study the effect of the ionic strength: 10(-3) mol L-1, 10(-2) mol L-1, 10(-1) mol L-1 and 1 mol L-1. In addition to NaCl, the following concentrations of proteins (in this case, pure albumin) were considered: 0, 1 and 20 g L-1. Experiments were carried out at a temperature of 22 +/- 1 degrees C. Measurements were obtained at open circuit potential, (OCP). During other experiments, the applied potential was equal to -400 mV/SCE and the current density was measured. An integrated analytical approach was used in order to elucidate the synergy between mechanics and corrosion. The most interesting finding is that albumin changes the mode of synergy. At 0 g L-1 of albumin, the main synergistic term is the influence of mechanics on corrosion. On the contrary, at 20 g L-1, the main synergistic term is the influence of corrosion on mechanics. (c) 2012 Elsevier B. V. All rights reserved.