PERFORMANCE AND DURABILITY OF FINISHES ON PREVIOUSLY COATED CCA-TREATED WOOD

Wood treated with chromated copper arsenate (CCA) preservative is used extensively in many architectural applications. In this study, untreated and CCA-treated southern pine and hem-fir boards that had been finished with several finishes and then weathered for 2 years at 45 degrees facing south were cleaned, refinished, and exposed to the weather again. After exposure for an additional 2 years at 45 degrees facing south in Wisconsin and Mississippi, the durability of the finishes on weathered and refinished specimens was similar to that of the initial finish durability. The CCA treatment was shown to have a positive effect on the performance and durability of many finishes in the study. Little difference in finish durability was noted between 0.25 and 0.40 pcf CCA retention levels. Coating performance was generally better on CCA-treated hem-fir than on treated southern pine, regardless of CCA treatment levels. Finish failures occurred more rapidly in Mississippi than in Wisconsin, particularly surface discoloration. Within the coating groups, the overall durability and appearance were reflected by the following order: fully pigmented (film-forming paints and stains) > lightly pigmented (semitransparent stains) > unpigmented (transparent water repellents and water-repellent preservatives). This study demonstrated that CCA-treated wood is compatible with a variety of surface finishes and that the effects of the treatment enhance the performance life of those finishes, even after cleaning and refinishing.