Medical Devices

Exponent’s corrosion scientists and engineers routinely perform electrochemical testing of medical devices to evaluate the device’s expected in-vivo corrosion resistance. The majority of the tests are performed according to American Society for Testing and Materials (ASTM) standard ASTM F2129-04 for “Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices.” Other tests such as ASTM F746-04 standard for “Pitting or Crevice Corrosion of Metallic Surgical Implant Materials" can also be performed.

The tests, which are usually performed in phosphate-buffered saline solution, and at 37°C, allow for the determination of the open-circuit, rest, breakdown, and repassivation potentials. A measure of the pitting corrosion resistance of the device is given by the difference between the breakdown potential and the rest potential, while a measure of the device’s crevice corrosion resistance is given by the difference between the repassivation potential and the rest potential.

Because there is no established, or widely recognized, criteria for the absolute breakdown potential required to ensure that devices have acceptable in-vivo corrosion performance, it is recommended that predicate medical devices, with proven in-vivo performance, be used as a reference against which to evaluate the test device.

Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) is often used to evaluate the surfaces of the implantable devices before and after corrosion testing.

In addition Exponent provides clients with guidance regarding FDA submissions with respect to stress analysis, fatigue, and in-vivo corrosion and performs root-cause failure analysis investigations on implantable medical devices.

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