Long-term stake evaluations of waterborne copper systems

Abstract

Limitations on the use of chromated copper arsenate (CCA) have heightened interest in use of arsenic-free copper-based alternatives. For decades, the USDA Forest Products Laboratory has been evaluating several of these systems in stake plots. Southern Pine 38- by 89- by 457-mm (1.5- by 3.5- by 18-inch) stakes were treated with varying concentrations of acid copper chromate (ACC), ammoniacal copper borate (ACB), or acid copper formate (CF) and buried to one-half their length in plots within the Harrison Experimental Forest in Mississippi. Stakes treated with acidic formulations (ACC and CF) generally performed well at copper oxide retentions above 1.8 kg/m3 (0.11 lb/ft3), as did ACB-treated stakes containing 3.5 kg/m3 (0.22 lb/ft 3 ) CuO. However, even at retentions where median ratings and the average index of condition remained high for over 20 years, individual stakes occasionally failed in less than 10 years. The results suggest that occasional early failures caused by copper-tolerant fungi may be a concern for use of these treatments in ground contact.

Citation

Lebow, Stan; Hatfield, Cherilyn; Crawford, Douglas; Woodward, Bessie. 2003. Long-term stake evaluations of waterborne copper systems. Proceedings : ninety-ninth annual meeting of the American Wood-Preservers'' Association ... Boston, Massachusetts, April 27-30, 2003 : Volume 99. Selma, Ala. : American Wood-Preservers'' Association: Pages 142-149