The effects of pH and Cu:Mea ratio in alkaline copper quat (ACQ) solution formulation on the distribution of coppermonoethanolamine (Cu-Mea) complex species and Cu precipitation, and its infl uence on copper leaching from treated southern pine samples were investigated. Distribution of Cu in ACQ solution was studied by means of an equilibrium speciation model for aqueous systems (MINTEQA2). Conditions that favored a higher proportion of monovalent cationic complex, [Cu(Mea) 2-H ] 1 + , and precipitated copper as CuCO 3 (s), resulted in higher leach resistance in treated wood compared to conditions that favored the neutral copper complexes, [Cu(Mea) 2-2H ] 0 , and higher ligand copper complexes, [Cu(Mea) 3 ] 2 + , [Cu(Mea) 4 ] 2 + . Monovalent cationic Cu complex is maximized at a pH close to 9 with a Cu:Mea molar ratio of 1:4. Amounts of Cu leached at pH 9 were low compared to those at pH 12, where most of the Cu is present as neutral complex. Reduction of pH from 9 to 8 did not reduce Cu leaching, because of the lower cation exchange capacity of wood at the lower pH. Changing the Cu:Mea molar ratio to 1:3 at pH 9 significantly reduced the higher ligand complexes in the formulation and resulted in the majority of the copper being distributed as monovalent cationic complexes and some CuCO 3 (s) precipitation. These changes in 1:3 formulation signifi cantly reduced copper leaching compared to Cu:Mea ratios of 1:4 and 1:10.

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Canadian refractory wood species treated with micronized copper (MCu) wood preservative become mottled and streaky in appearance. To overcome this issue, the MCu system was modified by adding small amounts of monoethanolamine (Mea). The modified systems were evaluated to clarify the role of Mea in terms of leaching, corrosion, and mold resistance of MCu systems. The mottled and streaky surface on treated spruce was prevented at Mea/Cu molar ratios between 0.7 and 1.5. Copper leaching remained modest and was only slightly higher than that of MCu alone up to a Mea/Cu molar ratio of 1.2. However, adding even a small amount of Mea to the MCu formulation increased fastener corrosion compared with MCu. Protonated Mea increased as more Mea was added and was identified as the main corrosion-causing electrolyte in the system.

The effects of ammonia (NH 3 ) addition to monoethanolamine (Mea)-based alkaline copper quaternary (ACQ) on the predicted distribution of cupric (Cu 2q ) species in solution and copper leaching from treated wood were investigated. Addition of ammonia in higher proportions reduced the amount of neutral copper-Mea complex at high pH and increased the amounts of divalent copper-NH 3 complexes. At lower pH, the amounts of high-ligand copper-Mea complexes were reduced. These effects should promote better fixation and diminish copper leaching. However, ammonia addition also reduced the monovalent copper-Mea complex and the amount of copper fixed by precipitation at lower pH. This effect could, potentially, reduce fixation and leach resistance. Ammonia addition to the ACQ formulation from a Cu:Mea:NH 3 ratio of 1:4:0 (normal Mea formulation, pHs9) to 1:4:2 (pH

This study investigates the effect of the relative proportion of copper oxide (CuO) to didecyl dimethyl ammonium carbonate (DDACb) in an alkaline copper quat (ACQ) formulation on the rate of copper fixation or stabilization and the resistance of treated wood to leaching of copper and quat (DDACb) for different ACQ retentions in wood. Red pine, jack pine, and black spruce samples were treated with ACQ at concentrations of 0.6, 1, and 1.5 percent with CuO to DDACb ratios of 2:1 (the usual ratio for ACQ-D), 1:1, and 1:2. Red pine samples posttreated at 50°C were evaluated for rate of fixation by the expressate method. Conditioned samples of the three species were evaluated for the leaching of copper, and DDACb (red pine). At similar ACQ retentions, a decrease in proportion of copper in the formulation resulted in a substantial reduction in the time required for copper fixation. There was a significant decrease in the amount of copper leached for all three species studied with reduction of proportion of copper in the ACQ formulation. Improved fixation time and reduced copper leaching resulted from the lower copper retentions in the samples with lower relative proportions of copper in the formulations. The reduction in leaching was higher for samples treated with concentrations of 1 and 1.5 percent ACQ. The formulation having a 1:1 CuO to DDACb ratio appears to be the most promising, considering the positive effects of reduced copper ratio on copper leaching and fixation time and the minimal effect on DDAC leaching.