According to the US Food & Drug Adminstration (FDA) [Guidance from FDA on Non-Clinical Intravascular Stents ], medical implant devices need to be corrosion resistant to avoid premature failure and to limit possibly toxic corrosion products from adversely affecting the human body. The implants have to undergo characterization in the following categories: 1) pitting and crevice corrosion potential, 2) fretting corrosion and 3) galvanic corrosion. Electrochemical testing fulfills two of those requirements, pitting and crevice corrosion potential and galvanic corrosion. ASTM F2129 is suggested for pitting and crevice corrosion potential to evaluate the implant’s corrosion resistance. Differences in fabrication, heat treatment and even labeling can have a detrimental effect on the medical implant’s corrosion resistance. When the implant has more than one type of metal, ASTM G71 can be used to evaluate the potential for galvanic corrosion.

The FDA recommends that all implantable devices under go corrosion testing. However, no established corrosion resistance guidelines are provided. The FDA suggests using ASTM F2129 but the test does not provide a pass/fail criteria. It is up to the company to provide data that justifies the corrosion resistant abilities of the medical device. Therefore, the medical device company must provide corrosion data in their 510(k) submittal that supports their device.

Recently, the FDA has issued a “Guidance for Industry: Coronary Drug-Eluting Stents— Nonclinical and Clinical Studies” for public comment. This document covers possible recommendations for drug eluting stents, i.e. stents that have a coating that slowly releases a drug into the body.

Background
With respect to approval for metallic medical implant devices, the FDA had demanded that corrosion resistance be proven, however no established guidelines to do so were provided. The interpretation of corrosion resistance testing was widely fragmented. Established electrochemical techniques such as ASTM G61 (Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys) were employed by many to meet the testing requirements to prove corrosion resistance. However, interpretation of G61 afforded many variables resulting in data that could not be compared between testing laboratories. ASTM Committee F04 on Medical and Surgical Materials and Devices, formed in 1962, accepted the task of unifying the community at large with a standard test method.