Alkaline copper quaternary
Alkaline Copper Quaternary (also known as ACQ) is a water based wood preservative method. The treatment is made up of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Canada, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.
Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steel, according to American Wood Preservers Association (AWPA) test results . It is necessary to use double-galvanized or stainless steel fasteners in ACQ timber. Use of fasteners meeting or exceeding requirements for ASTM A 153 Class D meet the added requirements for fastener durability. The U.S. began mandating the use of non-arsenic containing wood preservatives for virtually all residential use timber in 2004.
Unless kiln dried, freshly treated ACQ lumber must be dried extensively before painting.
Modern versions have been developed which offer improved performance to those mentioned above. The American Wood Protection Association (AWPA) standards for ACQ require a retention of 0.25 pounds per cubic ft (PCF) for above ground use and .40 pcf for ground contact.
Chemical Specialties, Inc (CSI, now Viance) received U.S. Environmental Protection Agency's Presidential Green Chemistry Challenge Award in 2002 for commercial introduction of ACQ. Its widespread use has eliminated major quantities of arsenic and chromium previously contained in CCA.
- ACQ FAQ from the Forest Products Laboratory of the US Forest Service
- Information from the U.S. Environmental Protection Agency
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