Physical ageing effect on water uptake and adhesion of epoxy coatings by EIS and the blister test

In a previous work, it was shown that the physical ageing of organic coatings had a strong effect onto the water uptake process, leading to lower water uptake values at saturation. The service life of an organic coating can be related to the water content at saturation, that may induce corrosion of the substrate, but also to the adhesion that prevents direct contact between the substrate and the aggressive environment. In this work, the effect of physical ageing onto water uptake and adhesion of epoxy coatings onto aluminium is then investigated.A model epoxy coating (DGEBA/Jeffamine230) was applied onto aluminium panels and fully cured using adequate thermal cycles. Different amounts of physical ageing were created by controlling the cooling of the systems and measured thanks to modulated differential scanning calorimetry (MDSC). The coated panels were then immersed in sodium chloride solution (30 g.L -1) at different ageing temperatures. The water uptake was calculated using EIS thanks to the Brasher and Kingsbury relation and the diffusion coefficients were evaluated using the dual-Fick diffusion model.For different values of physical ageing and different amounts of water uptake, the adhesion was evaluated using the blister test method. The obtained results allow to discuss the effect of physical ageing onto the water uptake content and the adhesion of organic coatings.