A comparison of the corrosion of alkaline copper and micronized copper treated wood

IRG/WP 10-40515

M Kofoed, J N R Ruddick

With the replacement of chromate copper arsenate (CCA) by alkaline copper wood preservatives, there have been reports of increasing corrosion of metal fasteners and connectors in contact with treated wood. This may be explained by the presence of more mobile copper in the treated wood. One novel industrial response has been to develop a wood preservative based on an aqueous solution containing suspended basic copper carbonate and a co-biocide. This micronized copper preservative relies on the basic acidity of wood to release the copper which can complex with the wood components. As a consequence of the lower amount of mobile copper, the degree of corrosion should be significantly lowered, compared to the corresponding alkaline copper preservatives. The objective of this study is to examine the relative corrosiveness of micronized copper and alkaline copper treated wood to determine whether a significant reduction in corrosiveness is obtained. The interim results of the study have confirmed a significant reduction in the degree of corrosion on hot dipped galvanized fasteners as well as a lower rate of corrosion on bright (or common iron) fasteners. The levels of the corrosion of the micronized copper treated wood were similar to those observed for western red cedar, a durable wood that has been used in the past for decks and fences in British Columbia.


Keywords: metal corrosion, micronized copper preservative, ACQ, copper preservative treated wood, western red cedar

Conference: 10-05-09/13 Biarritz, France


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