Differences between Preserve CA and ACQ?

Preserve® CA and Preserve® ACQ

Viance Preserve CA and ACQ

  • CA-C is a copper-based wood preservative that has been used to pressure treat wood products worldwide. The first form of copper azole (CBA-A) was standardized by AWPA in 1995 followed by CA-B in 2002. CA-C was first standardized in 2009.
  • CA-C contains a soluble copper component as the primary biocide and two triazole fungicides propiconazole and tebuconazole as co-biocides to help control attack from copper tolerant fungi.
  • ACQ is a copper-based wood preservative that has been used effectively around the world for over 25 years and was initially introduced in 1987. ACQ was introduced to the US in 1992.
  • ACQ is composed of a soluble copper component and a quaternary ammonium compound (Quat) as a co-biocide.


  • Both are water-based wood preservatives.
  • Viance’s brands, Preserve CA-C and Preserve ACQ are both made from 100% recycled copper and are soluble formulations capable of penetrating deeper in the wood cells. Not all competitors’ products contain recycled copper.
  • Both leave a dry, paintable surface.
  • Because the appearance and performance of CA and ACQ treated wood is very similar, they have been used interchangeably in many instances. It is rare for the average consumer to notice any significant difference in appearance between CA and ACQ treated wood.
  • The EPA states, “These wood preservatives have lower toxicity profiles when compared to older wood preservatives."
  • Both preservatives meet the stringent industry standards of the American Wood Protection Association (AWPA), the leading authority on wood preservation science. Both are standardized by the AWPA for a wide variety of residential, commercial and agricultural construction projects including above ground exposed use (UC3B), ground contact general use (UC4A), freshwater immersion (UC4B), and salt-water splash applications (UC4B)
  • Both are field-tested, proven-to-last, accepted as an industry standard, and are building code compliant (IRC and IBC).
  • Both are NAHB Home Innovation Research Labs Green Certified Products for Resource Efficiency and are eligible to contribute points toward a building’s certification under the National Green Building Standard™ (NGBS).


    • The main difference between the two types of treated wood is the co-biocides that are used to combat copper tolerant fungi. Copper Azole uses a blend of azoles as the co-biocide. ACQ uses a quaternary ammonium compound (Quat) as a co-biocide.
    • The differences are few and any differences typically only affect the producers. When properly produced, the differences in the treated wood are insignificant to the point where the retailer and consumer will not notice.
    • The performance of CA treated wood and ACQ treated wood is basically equivalent when properly treated and used in the correct application. When choosing between CA treated wood and ACQ treated wood, the purchaser should consider the following:
      • Performance history of the treating company
      • Quality of the substrate treated and results of treatment
      • Support available

Fasteners and Connectors

CA and ACQ treated wood are in the “excellent range” as defined in the Corrosion Engineering Handbook. Viance provides the following guidelines regarding fasteners used with Preserve CA and Preserve ACQ treated wood:

  • Use building-code approved, corrosion-resistant fasteners and connectors suitable for use in pressure-treated wood.
  • For fasteners, use of hot-dipped galvanized (meeting ASTM A 153) or stainless-steel fasteners.
  • For connectors, use G185 hot-dipped galvanized connectors for exterior applications.
  • For Permanent Wood Foundations and corrosive environments, such as Coastal areas with saltwater spray, use code approved stainless steel fasteners and connectors.
  • CA and ACQ are not suitable for direct contact with uncoated steel or aluminum building products.


Preserve CA and Preserve ACQ treated wood are covered by a Lifetime Limited Warranty from fungal decay and termite attack when installed in accordance with applicable building codes. See details of their Lifetime Limited Warranty for terms and conditions.

More Information


Find the technical bulletin at this link.