Water uptake in free films and coatings using the Brasher and Kingsbury equation: a possible explanation of the different values obtained by electrochemical Impedance spectroscopy and gravimetry

被引：72
作者：
Lacombre, C. Vosgien [1 ]
Bouvet, G. [1 ]
Trinh, D. [1 ]
Mallarino, S. [1 ]
Touzain, S. [1 ]
机构：
[1] Univ La Rochelle, LaSIE UMR CNRS 7356, Lab Sci Ingn Environm, Ave Michel Crepeau, F-17042 La Rochelle, France
来源：
ELECTROCHIMICA ACTA | 2017年 / 231卷
关键词：
water uptake; Brasher and Kingsbury; gravimetry; EIS; DMA; SECM; DIFFERENT PAINT SYSTEMS; SOLID EPOXY COATINGS; ORGANIC COATINGS; CAPACITANCE MEASUREMENTS; BARRIER PROPERTIES; PART II; ANTICORROSION COATINGS; DIELECTRIC-PROPERTIES; FICKIAN DIFFUSION; POLYMER-FILMS;
D O I：
10.1016/j.electacta.2017.02.051
中图分类号：
O646 [电化学、电解、磁化学];
学科分类号：
081704 ;
摘要：
For many years, the water uptake in organic coatings was measured by EIS and/or gravimetry but differences in water content values were found in almost all studies. The Brasher-Kingsbury equation used in the electrochemical analysis (EIS) is often criticized because elementary assumptions may be unvalid. The origin of the discrepancy between both methods is still of interest because many questions remain open and this study aims to provide new insights to these questions. In this work, free films and coatings of a model epoxy-amine system were immersed in a 3 wt.% NaCl solution. The water uptake in free films was evaluated using gravimetric measurements and EIS, using the Basher-Kingsbury equation. The mass of free-films used in the EIS tests was measured and compare to gravimetric measurements while the water uptake (EIS) in free films was compared to that obtained with coatings. It was found that the mass increase of free films tested with EIS was in agreement with gravimetric measurements but was always lower than the water uptake obtained by EIS. Moreover, the water uptake in free films (EIS) was different from that obtained with coatings. In all cases, it was found that the Basher-Kingsbury equation overestimated the water uptake. It appears that the differences between EIS and gravimetric measurements can be analyzed in terms of geometrical effects. Indeed, the swelling in free films and coatings can be monitored by DMA and SECM during ageing. Finally, by mixing the experimental swelling data and the Brasher-Kingsbury equation, the same value of water uptake was obtained by EIS and gravimetry for coatings. (C) 2017 Elsevier Ltd. All rights reserved.
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收藏
页码：162 / 170
页数：9
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