Determining Efficacy and Persistence of the Wood Preservative Copper Chrome Arsenate Type C against The Wood Destroying Insects and Treated Wood Durability

Abstract

The wood preservative Copper chrome arsenate (CCA type C) is one of the most common wood preservatives in the world, its effectiveness depends on performance, leach resistance, depth of penetration and persistence within treated wood tissue. The persistence of the preservative copper chrome arsenate typeC within four species of treated wood using full-cell pressure technique (double vacuum and pressure) and fixation of the preservative at 45˚C and 75% R.H was investigated. Bioassay tests were carried out to evaluate the performance of CCA-C treated wood against biological destruction and wood borers infestation using the powder post beetles Lyctus africanus (Lyctidae: Coleoptera).The treated wood samples at a concentration of 3% showed high resistance and durability against L. africanus attack through a period of four years, also the treated wood exposed to leaching process for two weeks showed resistance to L. africanus, which confirms the successful fixation of the CCA within the wood tissue and was not affected by leaching process. For all the tested treated wood species, the samples were free of L. africanus attack and no exit holes were recorded. It was found that, despite the cutting off treated wood blocks and exposing the internal parts (cross-section) of the wood to the beetles to lay eggs, wood is still resistant to beetles’ infestation, which confirms the deepening of the preservative into treated wood, also the penetration depth of the preservative (CCA) inside the wood tissue was measured using Ferro-Cyanide Potassium as a copper reagent. It was observed that, the internal tissue color (cross-section) of the treated wood has been changed to brown as a result of the penetration of copper into the treated wood. According to elemental analysis of the concentration of CCA components within treated wood after 48 months, very large differences among all wood species in retaining of elements were observed. Arsenic is clearly the least stable element in wood tissue. copper was the most affected element by leaching for all wood species. However, the residual CCA level was sufficient enough to prevent attacks and decay by L. africanus. ), Consequently, the full-cell pressure technique with (vacuum 30 in Hg) and the positive pressure of (10 bar) can be considered successful to preserve hardwood species against wood borers attack and maximize the penetration depth of the preservative within wood tissue.