Impedance spectroscopic study of a steel electrode in condition of scalingand corrosion - Interphase model

In this work, impedance spectroscopy was used to follow the time-dependent modifications of the surface layers formed on a carbon steel exposed to a w ater with high content in salts (typically: Tunisian south-west waters). Se veral layers were identified starting from green rust (Fe(II)-Fe(III) hydro xysulfates), with the intermediate formation of black magnetite, and the fi nal formation of an outermost layer of brown oxyhydroxide of the FeOOH type . The relevance of the equivalent circuit describing the overall behavior w as established through selective modifications of the stratified layers and the response of the impedance diagrams to these modifications. Diffusion p henomena through the layers were shown to play a determining role in the be havior of the system. (C) 1999 Elsevier Science Ltd. All rights reserved.