Predicting the steady state thickness of passive films in order to\n prevent degradations of implant

Some implants have approximately a lifetime of 15 years. The femoral stem,\nfor example, should be made of 316L/316LN stainless steel. Fretting corrosion,\nfriction under small displacements, should occur during human gait, due to\nrepeated loadings and un-loadings, between stainless steel and bone for\ninstance. Some experimental investigations of fretting corrosion have been\npracticed. As well known, metallic alloys and especially stainless steels are\ncovered with a passive film that prevents from the corrosion and degradation.\nThis passive layer of few nanometers, at ambient temperature, is the key of our\ncivilization according to some authors. This work is dedicated to predict the\npassive layer thicknesses of stainless steel under fretting corrosion with a\nspecific emphasis on the role of proteins. The model is based on the Point\nDefect Model (micro scale) and an update of the model on the friction process\n(micro-macro scale). Genetic algorithm was used for finding solution of the\nproblem. The major results are, as expected from experimental results, albumin\nprevents from degradation at the lowest concentration of chlorides; an\nincubation time is necessary for degrading the passive film; under fretting\ncorrosion and high concentration of chlorides the passive behavior is\nannihilated.\n