Abstract
The objective of this study is to investigate the effect of surface processing on the natural weathering performance of coated wood. The surface processing of four different roughness categories (processed by planing, sawing, wire-brushing, and sanding) was used for treating wood substrates (Sugi: Cryptomeria japonica D. Don). A preservative semi-transparent coating was applied on the wood substrates and exposed to natural weathering for 7 years. The coated wood surfaces were assessed using color difference (JIS K 5600-4-6), water repellency index, and visual assessment (JIS K 5600-8-4 and JIS K 5600-8-5). The difference in surface processing influenced the coating weights and the degradation speed of the coatings. The water repellency index of rough-sawn specimens maintained more than 80 % up to 5 years of natural exposure and the specimens exhibited lower flaking throughout 7 years of exposure, which has higher performance than other processing. The results indicated rough-sawn lumber was effective surface processing to improve natural weathering performance of preservative semi-transparent coatings.
