ABSTRACT
References ............................................................................................................ 502
13.1 INTRODUCTION
The electrochemical impedance spectroscopy (EIS) technique differ from all other
techniques described in this book insofar as the properties of an electrode/electrolyte
system are evaluated as a function of the frequency of a small ac signal that is applied
at a fixed working point (E,I). In most studies of corrosion systems E ¼ Ecorr and I ¼ 0. Modern equipment allows collection of impedance spectra in a wide frequency range covering about 10 orders of magnitude. Evaluation of the experimental spectra
as a function of the frequency f of the applied ac signal in Bode plots, which are the
preferred display of EIS data (1), reveals one or more time constants in different
frequency regions. In Bode plots the phase angle F and the logarithm of the impedance modulus jZj are plotted vs. log f. The minima and maxima of F and their positions at certain frequencies are sensitive indicators of system properties and
their changes with changing experimental conditions.
