Chromated Copper Arsenate Preservative Treatment of North American Hardwoods. Part 1. CCA Fixation Performance

Summary

We have examined chromated copper arsenate (CCA) wood preservative fixation at two selected temperatures in seven common North American hardwood species: red maple (Acer rubrum L.), white birch (Betula papyrifera Marsh.), yellow poplar (Liriodendron tulipifera L.), trembling aspen (Populus tremuloides Michx.), red oak (Quercus rubra L.), basswood (Tilia americana L.) and American beech (Fagus grandifolia Ehrh.). The softwood red pine (Pinus resinosa Ait.) was included for comparison. CCA component fixation was monitored by the expressate method at both 21°C and 50°C under non-drying conditions. Hexavalent chromium (CrVI) and total Cr, Cu and As contents of the expressate were determined at different times during fixation. Based on CCA fixation results it was possible to divide the examined hardwoods into a fast fixing group (beech, red oak and red maple), intermediate group (white birch and red pine) and slow fixing group (aspen, yellow poplar and basswood). The variable fixation rates for the different species could not be directly related to different anatomical and chemical attributes of the studied hardwoods, although there was an apparent relationship with density with more dense species fixing faster than low density species. However, the species differences appeared to be mainly influenced by types and amounts of extractives in the woods. In red maple, extraction resulted in a slowing of the fixation rate, while the opposite effect was seen in red oak.