Review on the durability of exterior wood coatings with reduced VOC-content

The main factors that contribute to the durability of exterior wood coatings are discussed with special emphasis on the recent developments to reduce the volatile organic compound (VOC) content in these types of coating like water-borne acrylic dispersions, water-borne alkyds or high solid alkyd formulations. The performance of a coating during outdoor weathering is determined by: photochemical degradation (only for paints that are not opaque), moisture permeability in relation to wood-moisture content and dimensional change and the microbiological degradation at the wood–coating interface. The results from various outdoor weathering studies are discussed. These studies show fairly consistent results with respect to the influence of coating type or wood species. However, a sound theory about the mechanism of failure, that can related to basic properties of the coating or the binder, has not yet been established.