Copper azole
Copper azole (CuAz/MCA) is a copper-based, arsenic-free timber preservative that replaced CCA for residential use, rated for outdoor hazard classes under AS 1604.
Ask Chalkline about this →Copper azole (CuAz) is a copper-based timber preservative used as an arsenic-free alternative to CCA (copper-chromium-arsenic). It protects timber against decay and termites by combining copper (the main fungicide and insecticide) with an azole co-biocide, and it carries no arsenic, which is why it replaced CCA for residential and public-contact uses after CCA was restricted from indoor and child-contact applications in 2006. The micronised form, MCA (micronised copper azole), is the modern volume default for residential treated pine: a lighter green-brown colour with less surface migration and less fastener staining than CCA.
Copper azole is rated under AS 1604.1 for the outdoor hazard classes, typically H2 to H5 depending on the formulation, with the micronised MCA product common at H2 to H4. So you see it on decking and external above-ground timber (H3), and on posts and in-ground structural timber (H4 and up). For most residential orders the spec is just the hazard class (“H3 treated pine”) and the supplier delivers copper azole or ACQ as stocked. The hazard-class-to-application mapping is non-negotiable: AS 1684 sets the minimum class for each location, and the certifier checks the stamp.
Like all copper-based treatments, copper azole reacts with bare mild steel and accelerates galvanic corrosion of fasteners and brackets. Use hot-dip galvanised (typically 600 g/m² minimum) or stainless steel fixings in copper-azole timber, and 316 stainless near the coast. Treat any cut end with a field preservative, because the cut exposes untreated heartwood. See treated pine.
Also known as: CuAz, MCA (micronised copper azole), CA-B / CA-C.
Category: Materials / Timber treatment.
Related
See also
References
- AS 1604.1:2021 Specification for preservative treatment, Standards Australia (verified 2026-05-13)
- Business Queensland: Using treated timber (verified 2026-05-13)
Last updated: 2026-05-30. Verified: 2026-05-13. Quarterly review for currency.