Electrochemical characterisation of electrodeposited organic coatings

Abstract

The electrochemical impedance spectroscopy and the potentio- static polarization techniques have been used to characterize the organic coatings electrodeposited on carbon steel. The coatings were formed during the cathodic and anodic electrodeposition of the modified epoxy resins on carbon steel samples previously polished and degreased (no primer was used). The experiments were conducted in stagnant, natural aerated 3% NaCl solution under ambient conditions. Analysis of the impedance spectra has established that an electrical equivalent circuit with two time constants fits to describe the electrodeposited epoxy coating/carbon steel system in the electrolyte solution. For the characterisation of the electrode- posited epoxy coatings the physical properties obtained from the principal elements of the equivalent electrical circuit and the electrochemical parameters obtained from the anodic polarization curves were used. It was established that these coatings present good performances characterized by low porosity, low water uptake and few conductive pathways and therefore a high efficiency. The coatings present a good adhesion to the carbon steels substrate; during the exposure period (60 days), no degradation or delamination process could be observed. © WILEY-VCH Verlag GmbH.