Abstract
As the biocompatibility of metallic implant materials is closely related to their corrosion behavior, the recognition of the advantages and limitations of routinely used corrosion tests is of primary importance. While electrochemical techniques provide invaluable information about the most relevant performance issues, the interpretation of the result obtained by these techniques may require more complex electrochemical considerations than usual in the case of less corrosion resistant metals and alloys. Additionally, the use of nonelectrochemical techniques such as metal ion concentration measurements and particle size characterization methods is often necessary to properly predict the magnitude of the overall electrochemical interactions between the metallic implant and the environment. In this paper, a coherent treatment of implant metal corrosion is given by reviewing the most important issues such as the fundamental theoretical and experimental considerations, the interpretation of the results of electrochemical measurements, the effects of mechanical and chemical breakdown of passivity, and the spontaneous passivation of major orthopaedic implant alloys. Due to the complexity of events that may take place in the harsh biological environment, in vitro experiments can not be expected to make the in vivo evaluation of these alloys unnecessary. Nevertheless, properly conducted in vitro studies can be very useful for making relative rankings, and for interpreting the clinical findings more reliably.
