Corrosion in the Human Body: Metallic Implants in the Complex Body Environment

Metals and alloys have been used in the human body as biomaterials to repair, replace, or augment tissues and structures for many decades. A principal concern in the use of metals in the body is the corrosion behavior of these materials. Titanium-based, cobalt-chromium-molybdenum-based, and stainless steel-based alloys comprise the preponderant metals used in orthopedic, dental, and cardiovascular medical devices across a wide range of applications. Each experiences challenging and unique environments. These environments include the electrochemical environment developed by the living system (i.e., the biological environment) and the mechanical environment. This article will provide a brief overview of the nature of the corrosion and tribocorrosion processes present in the human body by focusing on implant retrievals. Examples of corrosion damage in retrieved medical devices will be described and some of the underlying mechanisms and processes of corrosion will be presented. These include tribocorrosion processes and the role that inflammatory species play on corrosion attack. Some unique elements of corrosion in the human body will be discussed including the active response of the biological system to corrosion reactions (oxidation and reduction), and the effect of biological processes on corrosion will be presented.