Role of pretreatments in the protection of wood surface and finishes in the weathering of Pterocarpus marsupium wood

Wood samples of Pterocarbus marsupium (bijasal) treated with aqueous solutions of ammoniacal copper ferricyanide, acid copper chromate, acid copper chrome arsenate, ammoniacal copper chromate and ammoniacal copper chrome ferricyanide were studied for outdoor weathering. The treated and untreated wood samples were coated with three type of commercially available wood finishes, viz. polyurethane finish, synthetic enamel and acrylic emulsion paints, before exposing to the outdoor. Paint performance was studied for different periods of outdoor exposure. Results indicated that pretreatment of wood surface with the inorganic salt solutions helps in imparting water repellency and dimensional stabilization to the wood, resulting in increased service life of opaque and transparent coating over it. These treatments also slow down the photo-degradation of wood surface and inhibit fungal growth over it. Out of the five treatments used, the acid copper chromate provided the best protection to outdoor exposed wood surface.