Some Advantages and Pitfalls of Electrochemical Impedance Spectroscopy^☆

The use of electrochemical impedance spectroscopy (EIS) in corrosion research is briefly reviewed with particular emphasis on the advantages offered by this technique over other electrochemical methods. These advantages include the fact that it is a steady-state technique, that it employs small signal analysis, and that is capable of probing relaxations over a very wide frequency range (<1 mHz to >1 MHz) using readily available istrumentation. EIS also has the enormous advantage over classical transient techniques in that the validity of the data is readily checked using the Kramers–Kronig transforms. The principal pitfall of the method is the tendency of many workers to analyze their data in terms of simple equivalent electrical circuits, and hence to ignore the great power of EIS for deriving mechanistic and kinetic information for processes that occur at a corroding interface.