Use of a.c. impedance methods to study the corrosion behaviour of implant alloys

The a.c. impedance method is a very useful technique for studying the corrosion behaviour of surgical implant alloys. In this article information is presented on how to efficiently and reliably acquire and analyse experimental data through the use of Nyquist, Bode and Rre versus omega Rim plots. Also, experiments were conducted in which 316L stainless steel specimens were subjected to polarization conditions which caused pitting corrosion. The increased surface area caused by the pitting, inferred from a.c. impedance measurements of specimen capacitance, was found to be well correlated with ASTM standard methods for assessment of pitting.