The growth of the capacitance of organic coatings during immersion in aqueous solutions can be monitored by electrochemical impedance and has long been associated with the inward diffusion of water. For the drying stage, however, the absence of a liquid conducting medium has inhibited the application of the classical impedance methods. This work presents a novel approach, in which an ionic liquid is used as conducting medium to allow the coating to dry while the process is followed by single frequency impedance measurements. The diffusion coefficients for the water ingress and egress were determined. (c) 2005 The Electrochemical Society.