SEDL / STP / STP1188-EB / STP18082S

Electrochemical Impedance of Coated Metal Undergoing Loss of Adhesion

Kendig, MW
Technical staff member, senior technical specialist, and technical staff member, Rockwell International Science Center, Thousand Oaks, CA

Jeanjaquet, S
Technical staff member, senior technical specialist, and technical staff member, Rockwell International Science Center, Thousand Oaks, CA

Lumsden, J
Technical staff member, senior technical specialist, and technical staff member, Rockwell International Science Center, Thousand Oaks, CA

Pages: 21    Published: Jan 1993

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Abstract

A critical analysis of the concepts used to correlate parameters determined from electrochemical impedance spectra to the evaluation of the loss of adhesion of an organic coating from steel is made. In particular, the breakpoint method is called into question based on a theoretical analysis of the double layer capacitance of the coating/metal interface. A model for a coating undergoing disbonding about a macroscopic defect is described. The impedance of a fusion-bonded epoxy (FBE) pipeline coating about a large defect is considered in light of this model. The observations approach characteristics predicted by the model.