In addition to aesthetic appeal, coatings are designed to protect the wood from weathering degradation in outdoor conditions. This paper gives an overview of the effects of main components of coating, coating properties, and wood treatments on coating performance. Understanding how different type of resins (alkyd, acrylic or polyurethane), amount of pigments, type of solvents (organic or water), and major additives will affect coating performance on wood, helps coating formulators to develop more durable coatings. It is beneficial for both wood scientists and coating chemists to learn which properties of coating has the highest impact on predicting its service life when exposed to weathering. For instance, measuring glass transition temperature (Tg) will define the degree of flexibility of a coating. Since wood swells and shrinks due to moisture uptake and subsequent drying; therefore, flexibility of a coating plays a critical role in defining its durability on wood in exterior conditions. Or learning how a new preservative formulation or a new modification technique changes the surface properties of wood will help coating formulators to develop more suitable coatings for that specific modified wood. An example will be given on why coatings that were formulated for chromated copper arsenate treated wood were not as effective when applied on Cu-based or heat-treated wood. Also, how these factors can help to increase the service life of exterior wood coatings will be further discussed.

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