Validation of electrochemical impedance measurements for water sorption into epoxy coatings using gravimetry and infra-red spectroscopy

PHILIPPE, L. V. S., LYON, S. B., SAMMON, C. and YARWOOD, J. (2008). Validation of electrochemical impedance measurements for water sorption into epoxy coatings using gravimetry and infra-red spectroscopy. Corrosion Science, 50 (3), 887-896.

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Abstract

In this paper, the sorption/diffusion of water from an aqueous electrolyte into a commercial epoxy paint coating was compared using gravimetry, electrochemical impedance spectroscopy (EIS) and attenuated total reflection infra-red spectroscopy (ATR-IR) techniques as a function of electrolyte composition. All three techniques show an apparent two-stage diffusion process. Diffusion coefficients for water sorption obtained by ATR are consistent with those obtained using (conventional) gravimetric methods and impedance spectroscopy (EIS). We discuss the methods used to derive diffusion coefficients, and concentration of the sorbed species, from capacitance measurements. As such, we postulate that the cause of anomalous diffusion behaviour is due to the fact that the penetrant enters the polymer because of classical diffusion down the concentration gradients, which are modified a result of the time dependence of the surface concentration. Hence, an apparent two-stage sorption profile is not necessarily significant in a heterogeneous coating and Brasher's equation remains the most appropriate for data analysis. (C) 2007 Elsevier Ltd. All rights reserved.

Item Type:	Article
Research Institute, Centre or Group - Does NOT include content added after October 2018:	Materials and Engineering Research Institute > Advanced Coatings and Composites Research Centre > Polymers, Composites and Spectroscopy Group
Identification Number:	https://doi.org/10.1016/j.corsci.2007.09.008
Page Range:	887-896
Depositing User:	Jill Hazard
Date Deposited:	12 Apr 2010 09:23
Last Modified:	18 Mar 2021 21:15
URI:	https://shura.shu.ac.uk/id/eprint/1588

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