Characterisation of the barrier properties of different paint systems - Part I. Experimental set-up and ideal Fickian diffusion

The water uptake of a commercial alkyd paint system is studied using the im pedance spectroscopy technique. The first part of the paper is devoted to e stablish the experimental setup to accurately measure capacitance values in the pF range, characteristic of the studied system. It was concluded that electrochemical instrumentation is not adequate to perform this task. The s econd part of the paper discusses the water uptake of the paint system unde r two different immersion conditions: deionized water and 5% NaCl solution. This analysis leads to the conclusion that the diffusion process seems to follow the ideal-Fickian behaviour in both systems, the corresponding diffu sion coefficients were calculated. (C) 1999 Elsevier Science S.A. All right s rreserved.