Efficacy of waterborne copper naphthenate as preservative for northern hardwood species
D P Kamdem, R Fair, M H Freeman
Northern red oak (Quercus rubra) and red maple (Acer rubrum) cubes pressure treated with waterborne formulation of copper naphthenate were evaluated for resistance to attack by brown fungi Gloeophyllum trabeum (Pers. ex Fr.) Murr. (Madison 617 ATCC 11539) and Poria placenta (Fr.) Cooke (Madison 698, ATCC 11538), white rot fungi Trametes versicolor (L. ex Fr.) Pilat (R-105 from Jeff Morrell), Irpex lacteus Fries (FP-105915 from Jeff Morrell) and Pleurotus ostreatus (Jacq. ex Fr.) Kummer (ATCC 32237), and soft rot Chaetomium globosum (ATCC 34152) and Phialophoria sp. (from Dr. B. Goodell, University of Maine). Wood samples measuring 19 x 19 x 19 mm³ were pressure treated to target copper retentions of 12.48 kg/m³ (0,78 pcf), 9.77 kg/m3 (0.61 pcf), 5.6 kg/m³ (0.35 pcf), 4.5 kg/m³ (0.30 pcf), 2.56 kg/m³ (0.16 pcf), 1.2 kg/m³ (0.075 pcf), 0.48 kg/m³ (0.03 pcf). Data from laboratory soil block tests indicate that at 2.0 ± 0.5 kg/m³ (0.13 pcf) copper retention from waterborne copper naphthenate, the protection is similar to that from a 1.6 kg/m³ (0.10 pcf) elementar copper from oilborne copper nathenate or 7.2 kg/m³ (0.45 pcf) total oxide from CCA-C. Higher copper levels (3.0 ± 0.2 kg/m³) are needed to protect against copper tolerant brown rot fungus Poria placenta. Results from an American Wood Preserver's Association standard leaching test on samples treated with waterborne copper naphthenate show that 10 to 20% of the copper initially absorbed is leached and the amount of copper leached increases with the pH of the leaching solution or with the copper loading in the samples.
Keywords: COPPER NAPHTHENATE; CUNAPSOL; BIOLOGICAL RESISTANCE; DECAY; BROWN ROT; WHITE ROT; SOFT ROT; LEACHING; QUERCUS RUBRA; ACER RUBRUM