Effect of Prestain on the Release Rate of Copper, Chromium, and Arsenic from211 Western Hemlock

摘要

To enhance appearance, stains are often sprayed onto western hemlock (Tsuga211u001eheterophylla (Raf.) Sarg.) lumber prior to treatment with chromated copper 211u001earsenate (CCA-C). Recently, concerns have increased that prestaining may affect 211u001ethe rate of leaching of CCA-C components from the treated wood and that leaching 211u001edata generated with prestained material may not reflect the rate of release from 211u001enonstained wood. A secondary concern is that copper naphthenate field treatments 211u001eapplied to wood exposed during construction may contribute to the amount of 211u001ecopper released from CCA-C-treated structures. This paper describes a study in 211u001ewhich the release of copper, chromium, and arsenate was compared with end-matched 211u001enonstained and prestained CCA-C treated specimens exposed to artificial 211u001enonstained and prestained CCA-C treated specimens exposed to artificial rainfall. 211u001eThe effect of copper naphthenate and coating on release of copper was also 211u001eevaluated. The application of prestain prior to CCA-C treatment reduced the 211u001erelease rate of arsenate from the treated wood by approximately 28%. Most of the 211u001edecrease in leaching appeared to occur early in the test, during the time when 211u001earsenic release was greatest.