Abstract
Electrochemical Impedance Spectroscopy (EIS) is a widely used technique to study the organic coatings degradation. Thanks to capacitance measurements in the high frequency (HF) domain, EIS allows measuring the water uptake into the coating, using different models. Usually, a three electrodes cell is used to perform such measurements but if the sole HF domain is considered to assess the water uptake during the beginning of the immersion period, then the reference electrode (RE) can be deleted and a two electrodes cell can be used. In this work, model epoxy coatings (DGEBA/DAMP), with or without pigments (TiO2), were prepared as free films or were applied onto steel panels (Q-Panel). The different samples were immerged in a NaCl 3 wt% saline solution and water uptake was followed by EIS using a two or three electrodes cell. EIS spectra obtained without RE show new time constants in the HF domain which can be related to intrinsic properties of the system. This leads to a better understanding of the water uptake phenomenon into organic coatings and offers the possibility to modify well-known water uptake models.
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