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Chromated Copper Arsenate (CCA):
ACQ - An Alternative to CCA
CCA Table of Contents
Description and Formulations of ACQ
ACQ is a water-based wood preservative that prevents decay from fungi and insects (i.e., it is a fungicide and insecticide). There are currently four AWPA standardized ACQ formulations, ACQ Types A, B, C, and D. The different formulations allow flexibility in achieving compatibility with different wood species and end use applications. All ACQ types contain 2 active ingredients which may vary within the following limits: copper oxide (62%-71%), which is the primary fungicide and insecticide, and a quaternary ammonium compound (29%-38%), which provides additional fungicide and insect resistance properties.
- ACQ-A: Standardized by the American Wood-Preservers' Association (AWPA)1 in 1992 and deleted in 2000 due to a lack of use.
- ACQ-B: Standardized by the AWPA in 1992 and is primarily used for the treatment of western wood species such as Douglas fir because its ammonia carrier solution allows the ACQ to penetrate into these difficult-to-treat species. This formulation contains 66.7% copper oxide and 33.3% quat as didecyldimethylammonium chloride (DDAC). ACQ-B treated wood has a dark greenish-brown color that fades to a lighter brown and may have a slight ammonia odor until dry.
- ACQ-C: Standardized by the AWPA in 2002, it contains 66.7% copper oxide and 33.3% quat as alkyldimethylbenzylammonium chloride (ADBAC). Ammonia and/or ethanolamine can be used as the carrying solution in this formulation. Wood treated with ACQ-C varies in color that ranges between that of type B and type D.
- ACQ-D: Most wood-treating plants in the US generally use the ACQ-D formulation except for much of the west coast. Standardized by the AWPA in 1995, ACQ-D contains 66.7% copper oxide and 33.3% quat as DDAC. Type D differs from type B in that it uses an ethanolamine carrier solution rather than ammonia. Wood treated with ACQ-D has a lighter greenish-brown color with little odor.
Applications of ACQ
Water-based preservatives like ACQ leave a dry, paintable surface. ACQ is registered for use on: lumber, timbers, landscape ties, fence posts, building and utility poles, land, freshwater and marine pilings, sea walls, decking, wood shingles, and other wood structures.
1 The American Wood-Preservers' Association (AWPA) is the primary standard-setting body for pressure-treated wood. To become standardized by the AWPA, preservative-treated wood must undergo a series of rigorous tests to ensure its durability.