An investigation into the potential of ionic silver as a wood preservative

Abstract

On December 3 1, 2003, the wood preservation industry, in conjunction with the Environmental Protection Agency, voluntarily phased out the use of chromated copper arsenate (CCA)-treated lumber for residential applications. This ended over 25 years of CCA as the predominant wood preservative in the United States. The first generation of replacement preservatives, alkaline copper quats (ACQ) and copper azole (CA), has begun to replace CCA in 2004. Other potential replacements for CCA are under investigation at the Forest Products Laboratory (FPL). One of these, recently mandated by the 108th Congress, is the use of wood preservatives based upon silver (Ag) instead of copper. Silver has been shown to have potential as a viable, safe, and cost-effective preservative. The FPL has initiated a feasibility study of ionic silver salts for inhibition of brown-rot fungi, termite damage, and mold contamination. To date, two silver formulations (~ 1% Ag) have been shown to be moderately resistant to brown-rot decay, to inhibit termite damage with 100 percent mortality of termites, and to resist colonization by three common mold species. Additional testing, including American Society for Testing and Materials leach testing and lower silver concentrations, further explore the potential of silver-based biocides as wood preservatives. We conclude that potential silver-based biocides should be investigated further to determine minimum inhibitory concentrations for fungal decay and termite damage.

Citation

Dorau, Benjamin; Arango, Rachel; Green, Frederick. 2004. An investigation into the potential of ionic silver as a wood preservative. Proceedings from the Woodframe Housing Durability and Disaster Issues Conference : October 4-6, 2004 ... Las Vegas, Nevada, USA. Madison, WI : Forest Products Society, 2004: Pages 133-145.