An application of impedance techniques to corrosion research on dental amalgam

AC impedance techniques are finding increasing application in corrosion research. It was our aim to introduce them as a method for the evaluation of the electrochemical behaviour of dental amalgam. The complex plane plots are large depressed semicircles representing the frequency dependence of the impedance and measured at the corrosion potential. Conventional dental amalgams, in a chloride medium, exhibit a current peak in the proximity of -250 mV (vs. SCE). The corresponding impedance spectra are rather complex and difficult to interpret. The high frequency part, however, can be fitted to a semicircle with its centre lying below the real axis. An evaluation of the corresponding 'charge transfer resistance' shows that it is inversely proportional to the corrosion current density.