Chromium in Timber Preservation
Description
Chromium in Timber Preservation
prepared by Dr. Richard Murphy, Department of Biology, Imperial College of Science, Technology and Medicine, London. |
• Introduction Chromium compounds have been used in the formulation of water-borne wood preservatives for about a century. They function as essential chemical fixatives for the copper and other fungicidal and insecticidal components in the widely used chromated-copper preservatives, of which the best known example is CCA (copper-chrome-arsenic). Studies have shown that chromium in these preservatives has little or no direct action against decay fungi. However, stabilisation of the other preservative components achieved through valency state reduction of chromium makes them resistant to leaching and provides the treated wood with long-term durability against fungal and insect attack, even in high risk environments. Recent research and development efforts have led to the introduction of controlled and accelerated fixation systems which provide CCA treated timber products having very high degrees of fixation (>99%) of the chromium, copper and arsenic components. The development, functional role, safety and environmental aspects of chromium containing wood preservatives are summarised in this article. |
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