Work

Water vapor transport in cataphoretic coating and its associated multilayer system

Year: 2025

Type: article

Abstract: The water transport properties of an automotive paint system were characterized. First, we focused on epoxy-based cataphoretic free films and the corresponding multilayer paint system, consisting of a clearcoat, two basecoats, and the cataphoretic coating. The temperature dependence of diffusivity was highlighted by measuring water uptake at 30 °C, 50 °C, and 70 °C. The activation energy was found to range from 52 kJ/mol to 26 kJ/mol, depending on relative humidity. Water concentration at saturation was measured as a function of relative humidity across the temperature range. Sorption isotherms exhibited a linear behavior consistent with Henry’s law up to 50% relative humidity, followed by a positive deviation beyond this threshold. This deviation was attributed to the formation of water clusters, whose size was subsequently quantified. The cluster size increased significantly beyond 50% relative humidity ( i.e. , 0.5 water activity) and appeared to be only slightly influenced by temperature.

Source: Progress in Organic Coatings

DOI: 10.1016/j.porgcoat.2025.109479

Authors: Hiba Lazeregue, Cyrille Sollogoub, Stéphane Delalande, Jean-Charles Menetrier, Raynald Bougnot, Bruno Fayolle