Corrosion studies of stainless steel 316L, modified by ion beam techniques, under simulated physiological conditions

Abstract

Stainless steel 316L is a commonly used material for medical implants in orthopaedic surgery. In order to improve its performance in biological surroundings, metallic coatings (Au, Ag, Cu and Zn) were deposited by evaporation (vapour deposition) followed by ion beam mixing. Ceramic coatings (Al 2O 3) were produced by ion beam-assisted deposition. As protection against galvanic corrosion of the 316L bulk material in contact with noble metals, an alumina layer was deposited on to the bulk material and afterwards the coatings with noble metals were carried out. Potentiostatic and potentiodynamic corrosion experiments in physiological sodium chloride solution and in human plasma showed interesting differences in the corrosion behaviour between these two electrolytes. Coatings with a high corrosion protection in human plasma sometimes showed poor corrosion protection in physiological sodium chloride solution. These findings are discussed on the basis of the electrochemical properties of the systems. The combination of alumina and silver coatings showed the best results in electrochemical corrosion evaluations in both solutions.