Experiences with penetration of copper-based wood preservatives
J Jermer, F G Evans, I Johansson
In the Nordic countries there is a long tradition of result type based specifications for preservative-treated wood. A common Nordic standard for treated pine (Pinus sylvestris) wood was published in 1976. After a revision in 1989 this standard, then named INSTA 140, defined four classes of treated wood: M, A, AB and B. Treaters producing according to this standard had to be affiliated to a quality control and certification scheme. When the European standards EN 351 and EN 599 were to be implemented, the Nordic Wood Preservation Council issued a Nordic application document where the traditional wood preservation classes were defined in terms of EN 351 and EN 599. The present paper describes briefly how the European standards have been implemented in the Nordic countries. During the last years the use of CCA-preservatives has been restricted in the Nordic countries. New copper-based, chromium and arsenic free preservatives have been introduced for commodities above ground. This has by no means been without complications. The treaters have had severe problems to comply with the treatment requirements. Pilot plant treatment trials confirm that the penetrating properties of the chromium/arsenic free preservatives differ substantially from CCA. Experience from the Nordic quality control and certification scheme shows that it is often difficult to judge the penetration of the chromium and arsenic free preservatives. Different copper reagents give different results. A comparative test showed that ammoniumhydroxide and rubeanic acid as reagent for copper was the most sensitive to copper and performed better than other reagents tested.