Bror Häger, Gary C. Johnson, John D. Thornton, W. David Gardner
The Condition, after 31 Years Exposure, of Pine Stakes Treated with Ammoniacal Copper-Based Preservatives
Summary
Pinus sylvestris sapwood stakes were treated with various copper–containing waterborne and oilborne preservatives and exposed in ground for 31 years at Walpeup, Australia. Most of the waterborne preservative treatments contained basic copper carbonate and one or more of the following additives: arsenic pentoxide, pyridine, sodium pentachlorophenate, tannin and benzoic, boric, chromic, salicylic and sorbic acids. Basic copper carbonate and sulphate, at 0.95 kg m?3 of copper, protected the stakes from significant subterranean termite attack at a site in Australia providing a moderate termite hazard. Three additives (arsenic pentoxide at 0.95 kg m?3, sodium pentachlorophenate at 0.93 kg m?3 and fluoride at 0.9 kg m?3) significantly improved the efficacy of basic copper carbonate when used at retentions of 1.7 to 2.0 kg m?3 of copper. The six waterborne preservative combinations that performed best (i.e. rating greater than 6.5 out of 8) against both the termite and decay hazards over the 31 year period contained basic copper carbonate (at least 1.79 kg m?3 of copper) plus arsenic pentoxide (at least 0.92 kg m?3). Three of the six combinations also contained chromic acid. The oilborne preservative combination performing best contained basic copper carbonate (1.33 kg m?3) and pentachlorophenol (6.64 kg m?3) in tall oil. A treatment containing a similar amount of pentachlorophenol in tall oil, but no basic copper carbonate was significantly less effective. Other treatments containing basic copper carbonate and pentachlorophenol in tall oil or the copper compound with sodium pentachlorophenate in oil emulsion performed well. The implications of these results for the current generation of copper-based preservatives are discussed.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 55, 02/2001
Pages: 163 - 170
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