In response to concerns over the environmental safety of Copper Chrome Arsenate (CCA) treated timber over its entire life cycle, timber preservative treatment manufacturers have developed several alternatives. One of these uses copper and an organic azole co-biocide as active ingredients. It is currently marketed in Australia as "E" type preservative.
Similarly to CCA, the treatment process for copper azole preservatives involves impregnating the sapwood with preservative by a vacuum/pressure process in specially designed treatment plants.
Current approval has been granted in AS1604 for use of timber treated with copper azole preservatives in Hazard Classes 3 and 4. This covers the majority of above and in-ground applications for construction, external decking, landscaping, fencing and agricultural use, but not piling, house stumps or retaining walls.
Timber treated with copper azole preservative is initially coloured green, but weathers to brown. As with all timber, if it is used in exposed applications it should be protected by paint, stain or water repellent coatings.
Fasteners used in treated timber should be hot-dip galvanised, nickel coated or stainless steels. Alternatively, non-ferrous fasteners perform satisfactorily. Note that contact between timber treated with copper based preservatives and zincalume roofing may cause pitting of the metal coating.
Freshly cut surfaces of preservative treated timber should be coated with timber preservative solution, as the cut may expose unpenetrated heartwood.
Reference: Brochure: "Frenchpine E Pressure Treated Timber"
