SYMPOSIA PAPER Published: 01 January 1993

The Impedance Response of Film-Covered Metals


This paper derives the expected electrochemical impedance response of a corroding film-covered metal. The film is assumed to be nonelectroactive and uniform corrosion and transport by diffusion are considered. A generalized equivalent circuit for such a corroding system is presented. All terms in this equivalent circuit are defined by physical, chemical, or electrochemical constants of the system, which applies constraints to the possible values of equivalent circuit elements. It is shown that use of expressions derived for redox systems at their equilibrium potential can introduce significant errors in the analysis of data from corroding metals. The correlation between corrosion rate and polarization or charge transfer resistance is also discussed.

Author Information

Turgoose, S
Corrosion and Protection Centre, UMIST, Manchester, United Kingdom
Cottis, RA
Corrosion and Protection Centre, UMIST, Manchester, United Kingdom
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Developed by Committee: G01
Pages: 173–191
DOI: 10.1520/STP18069S
ISBN-EB: 978-0-8031-5240-3
ISBN-13: 978-0-8031-1861-4