Metal Corrosion in the Human Body: The Ultimate Bio-Corrosion Scenario

about until it becomes a personal health issue for most of us. That is, the need for the implantation of a medical device (Fig. 1) to improve our existing medical condition. The majority of these devices are made of a metal alloy (Table I), and for most of us, any concerns about corrosion implications from these implants are secondary to the relief we feel from the anticipated beneficial effect these devices are designed to have. As the global population increases in age, there is a parallel increase in the number of implantation procedures. One study reports that world-wide sales of orthopedic implants alone in 2003 was $8.7 billion and projected to increase at an annual growth rate of 12.5% and reach $17.9 billion by 2009.1 Clearly, as new devices and technologies are developed, there will be a continuing need for the understanding and characterization of how metal surfaces of implants interact with their surrounding physiological environment. Implant alloys are typically derived from three materials systems: stainless steels, cobalt-chromium based alloys and titanium alloys.2 The question “Does corrosion of a metallic implant cause a clinically relevant problem?” is one that probably only an electrochemist or materials engineer will ask when confronted with the prospect of having a metal device implanted into his or her body. While numerous issues may arise with the implant following surgery, one of the most fundamentally important is the interaction between the surrounding physiological environment and the surface of the implant itself. This interaction can lead to either the failure of the implant to function as it was intended, or have an adverse effect on the patient Metal Corrosion in the Human Body: The Ultimate Bio-Corrosion Scenario