ABSTRACT
The moisture transport in a composite coating system is one of the main factors affecting coating deterioration and corrosion of substrate under a marine environment. Based on C-M model and B-K equations which are used to describe the moisture transport in the single coating, both the gravity method and the capacitance method theoretical models of moisture transport in a multi-layer coating system are established. Moisture transport parameters of epoxy zinc rich primer, epoxy cloud iron intermediate paint, acrylic polyurethane top coat and their composite coating system in an environmental chamber with saturated environment are measured by using both the gravity method and the capacitance method. With the theoretical models, the influence of the diffusion coefficient ratio and dielectric constant ratio of adjacent coating layers are analyzed on moisture transport in composite coating system. It indicates that distinct stages during the moisture transport process in a composite coating system can be observed from the capacitance method theoretical model, while the saturated water sorptivity in each coating layer can be obtained from the gravity method. In order to accurately describe the moisture transport behavior in a composite coating system, both the gravity method and the capacitance method should be applied.
