The present work was aimed to develop multilayer coil coatings, superior to the currently available products by combining conventional and novel application and curing techniques such as radiation curing. Improved mechanical properties and durability can be achieved by high quality three layer thick film coatings. Because of the well-proven qualities of conventional primers and topcoats, all three-layer systems included the radcure coating as a mid layer. Applied as a midcoat, the potential risk of photocatalytic degradation due to unreacted photoinitiator remaining in the radcure coating is eliminated by the pigmented topcoat screening out the harmful sunlight. In addition, the subsequent curing of the topcoat provides a thermal post bake of the midcoat, resulting in further reaction of reactive groups, relaxation of the network and improved properties. Radcure formulations were tested between conventional polyester primers and topcoats on HDG and Galfan substrates. The effect of curing parameters on the degree of conversion and the final coating properties were evaluated. A clear improvement in the overall performance compared to the reference systems was observed. Also the corrosion protection was enhanced especially in the case of scribe down to zinc. The improved corrosion behaviour of the multilayer systems was also evident on the basis of the EIS-results.
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