Detection of Pitting on Cast Iron with AC Impedance Spectroscopy

Abstract

Abstract The pitting behavior of high-chromium cast iron has been studied with AC impedance spectroscopy. When impedance measurements are carried out at open circuit potentials, it is observed at the initial stage of pitting that with increasing time, the polarization resistance R decreases for the better pitting resistant specimen, and increases for the poorer one. However, when the electrode potential is suitably fixed during the measurements, the R value shows an abrupt decrease at the initial stage for the sample with a poorer pitting resistance. This large change in the R value indicates the initiation of the pitting process and thus can be used for detecting such onset.