Alkaline copper quaternary (ACQ) H3


Davids Timber are specialists in timber preservation offering ACQ H3 custom treatment produced to Australian Standards 1604. We can supply a full range of treated products or treat timber supplied by you.

ACQ treated timber has been used in some of the world’s most beautiful locations, like the pristine environments and National Parks in Australia, North America, Europe and Japan to neighborhood playgrounds and backyards.

ACQ Treatment Information

Alkaline Copper Quaternary (ACQ) Is a timber preservative made up of copper, a fungicide, and quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment.

What does each component do?

Each of the components play an important role in making ACQ an effective preservative.

  • Alkaline acts as a fungicide
  • Copper is an insecticide and a back-up fungicide
  • Quaternary acts as a “fixing” agent

These components reacting in the presence of wood cellulose to render the copper and arsenic chemicals insoluble. This “fixing“ mechanism involves a chemical reaction, with the formation of a complex mixture of insoluble chromium compounds.



ACQ treated timber will initially have a greenish appearance and will eventually weather to a honey brown colour before fading to a driftwood grey after exposure to the elements. Timber treated with ACQ can be painted or stained to match most outdoor colour schemes.

Where is ACQ used?

ACQ is widely used for applications such as;

  • Timber decking
  • Handrail
  • Playground equipment
  • Picnic tables
  • Furniture
  • Other high contact residential, commercial and industrial applications.


When using ACQ treated timber, we recommend the use of fasteners and other hardware which are in compliance with building codes for the intended use. The fasteners we recommend are quality hot dipped and stainless steel fasteners. Direct contact of ACQ with treated timber with aluminum is not

More Information

For all wholesale enquiries, please call us on (03) 9794 4777 or complete our Wholesale Enquiry Form. For all trade and retail enquiries, we recommend the following Treated Pine Stockists.

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