The effect of additives on copper losses from alkaline copper treated wood

IRG/WP 07-50246

J Mitsuhashi, J J Morrell, L Jin, A F Preston

The replacement of chromated copper arsenate (CCA) by alkaline copper compounds has heightened awareness of the potential impact of copper losses on aquatic organisms. While there remains a healthy debate concerning the actual risk of copper leaching from wood preservatives into aquatic ecosystems, it is clear that reducing these losses will be necessary to avoid continued regulatory actions against the use of preservatives in these environments. While post-treatment processing and coatings can reduce losses, neither is completely effective. Another alternative is to add compounds to the alkaline system to complex or otherwise reduce copper losses, much in the same way that chromium acts in CCA. One possible additive is Di(hydrogenated tallowalkyl) dimethyl ammonium chloride, also know as 2HT, which is a common fabric softener. Preliminary tests suggested that this compound reduced copper losses from alkline copper quat and, in doing so, improved overall biological performance. In this report, we describe additional trials to assess the effect of 2HT on copper migration from wood treated with either ACQ or copper azole (CA). 2HT had a variable effect on copper migration, but was associated with reduced copper losses in some treatment combinations. Further trials are underway to assess the biological efficacy of wood treated with combinations of 2HT and either ACQ or CA.

Keywords: chromated copper arsenate, alkaline copper quaternary, copper azole, leaching

Conference: 07-05-20/24 Jackson, USA

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