ASTM-F2129

Standard Test for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptability of Small Implant Devices.

BACKGROUND AND SCOPE

The FDA requires medical device manufacturers to submit a variety of test data to demonstrate efficacy and safety before a device can be implanted in patients. Corrosion is of concern for medical devices because it can both weaken the device and also cause adverse biological responses. Metallic devices that are permanently implantable are  assessed for corrosion resistance according to ASTM F-2129 Standard Test for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptability of Small Implant Devices.

In this case study, 3 devices that were subjected to 3 different processing conditions were evaluated in order to assess which condition produced the best corrosion resistance.

PROCEDURE

Each device was connected to the potentiostat and immersed in de-aerated Hanks Balanced Salt Solution, which was kept at body temperature. The potential was monitored for an hour to determine the rest potential (Er). Each device was then anodically scanned until the breakdown potential was reached, and cathodically scanned back to Er.

RESULTS

The potential is plotted against the log of the exchange current density as shown in figure 1. The following parameters are obtained from the plot: Er, Eb, Ep(For materials that exhibit a protection potential) , and Ezc.

 Figure 1: Plot of Exchange Current Density vs. Potential

DISCUSSION

Device#3 (blue curve) had a breakdown potential of over a volt, which was double the breakdown potential of the other two samples. The processing conditions for this device were ideal, and created a surface finish that was not as susceptible to corrosion as the other two samples.