A tannin/copper preservation treatment for wood

Abstract

Tannins are natural preservative agents found in many plant tissues but their low toxicity prevents their use as wood preservative on their own. However, they can fix biocides because of their excellent chelating properties. Co-impregnation in a two-step treatment of three biocides, copper, zinc and boron, with tannins is studied. Biocide leaching resistance and treated wood resistance to decay by rots and blue-stains are determined. Good retention of copper(II) ions is achieved by first impregnating wood with a commercial chestnut tannin. The treated wood meets the European standard for protection against rots. No protection against blue-stains was obtained as boron retention was not achieved.