Laboratory Corrosion Testing of Medical Implants

Performance evaluation of implantable devices is not new to medical device manufacturers, specifically implant manufacturers. A focus on corrosion resistance of implant devices has prompted members of the medical device industry, along with the United States Food and Drug Administration [USFDA] to set forth a guide for performance testing. Although actual corrosion resistance of a material can only be proven through long-term clinical trials, accelerated laboratory tests can be used to predict certain effects. Because corrosion of metals is an electrochemical process, accepted electrochemical testing techniques are used very effectively in the CPI (Chemical Process Industry) [namely ASTM G5, G61, and G71] have been adopted for use. Inconsistencies among laboratories, employing differing protocols, have resulted in varying interpretations by even the most experienced electrochemists and corrosion scientists. Some of the most widely used standard tests are also the most widely abused and misinterpreted, especially by persons who are less aware of materials properties. Since the USFDA provides no clear direction to testing, a modified electrochemical standard [ASTM F2129] has been adopted to address concerns regarding test environment, voltage scan rate, device configuration, and test protocol. The remaining issue is the establishment of an acceptance criterion.