Effect of curing characterization on the corrosion performance of polyester and polyester/epoxy powder coatings

In this study, effect of curing program on the corrosion performance of un-pigmented polyester and epoxy polyester powder coatings was evaluated, using various test methods. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) studies were carried out to determine suitable time –temperature curing program. Protective behavior of cured powder coatings in optimum situation was investigated, using different test techniques such as electrochemical impedance spectroscopy (EIS), water vapour transmission (WVT), and open circuit potential (OCP) variation as a function of time.EIS studies and OCP evaluation revealed that the polyester/epoxy powder coated samples demonstrated a better performance than polyester powder coated samples, due to higher cross-linked density of epoxy based powder. It is argued that these studies may provide sufficient evidence to show that protective characteristics of coatings is definitely influenced by cross-linking density so that more efficient coatings are ones with higher cross-link density.DMTA revealed that the different curing regimes do not affect the glass temperature of the given powder coatings.