Weathering Performance of Topcoats: Do Colours Matter?

Abstract Corrosion protective organic coating systems often consists of several layers comprising a variety of different coating products. The coating mostly responsible for improving and maintaining the visual aspects of the entire coating system is called a topcoat. Its durability is usually described with gloss and colour retention values, which characterize the change of both gloss and colour after certain exposure time. This paper presents weathering data of broadly categorized polyurethane and polysiloxane topcoats, and discuss their weathering performance with particular focus on the colour of the topcoat, and the type of pigmentation. The data was analysed on multiple levels: specific colours, binder technology, types of pigments and weathering tests. Overall, it was found that the light-coloured topcoats performed better in most tests, showing very good gloss retention and colour stability. Among other colours, those based on inorganic pigments were usually more resistant to weathering, compared to the more vivid colours with organic pigmentation. It was concluded that coatings with better gloss and colour retention could contribute to lowering the environmental and financial impact of the coated assets through increasing the maintenance-free service time.