Chapter 3: Corrosion of Metallic Implants

The practice of using metals and alloys to repair or replace human body parts is now well established. Two of the most important parameters in determining the suitability of a material for biomedical applications are its biocompatibility and corrosion resistance. This chapter gives a basic introduction to the thermodynamic and electrochemical aspects behind corrosion, concentrating on the various forms of localized corrosion that are responsible for most in-vivo failures. This will be followed by a brief review of the successes and, in reality, the remarkably few failures of the traditional materials: mainly titanium alloys, cobalt–chrome alloys, amalgams and stainless steels. The desire to make use of a number of advanced materials, such as memory-shaped alloys, porous materials and rare earth magnets will then be discussed. Unfortunately, nearly all of these materials have inadequate corrosion resistance to be used directly in vivo without some form of protection. The chapter ends with some case histories of surgical implant failures.