Electrochemical impedance spectroscopy studies of coated steel specimens in soils

Abstract

The electrochemical impedance spectra of specimens, cut from an epoxy-coated steel pipeline, in three soils in the Memphis metropolitan area were monitored over a 90-day period. The test soils were carefully selected to reflect the range of soil types found in this region. From the Nyquist and Bode plots generated, (a) the temporal variation of the low-frequency (IHz) impedance modulus and phase angle were obtained, and (b) an appropriate equivalent electrical circuit was identified, with it having the following elements: RSOIL (representing the soil resistance), CCOAT (representing the coating capacitance), RPORE (representing the resistance of pores in the coating), CDL (representing the capacitance of the double layer), RCT (representing the charge-transfer resistance), and WDIFF (representing the Warburg impedance).

Publication Title

Corrosion Prevention and Control

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