Weathering durability of chromium-treated southern pine

The purpose of this study was to compare the efficacy of chromated copper arsenate (CCA) and chromium trioxide treatments in decreasing the weathering of unfinished wood and imposing the durability of semitransparent and solid-color stains applied to the treated wood. Unfinished and finished southern pine sapwood specimens treated with either CCA or chromium trioxide were exposed to accelerated weathering. Small amounts of chromium salts on the wood surface greatly decreased weathering (erosion) of the wood caused by ultraviolet-light-catalyzed degradation. For unfinished wood, pressure treatment with CCA provided long-term protection against erosion. Treatment of the wood surface with a brush-applied solution of chromium trioxide also increased erosion, but not to the extent found for the wood treated with CCA. For finished wood, the CCA treatment greatly extended the lifetime and durability of a partially ultraviolet-light-transparent (semitransparent) stain. Stain durability on wood pretreated with CCA under pressure was superior to that on wood pretreated with brush-applied chromium trioxide; the CCA treatment penetrated the wood and deposited more chromium at the surface than did the chromium trioxide surface treatment.

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