Grey Wood Preserver

Old CCA charge carried arsenic and chromium and has been squeezed out of most Western markets. This grey wood preserver is a fourth-generation waterborne ACQ based on an alkyl-copper-quaternary complex, so railway sleepers, poles, landscape timber and farm buildings gain long service life without the heavy metals. On southern pine vacuum-pressure treated at 6.4 kg/m³ retention, an AWPA E10 soil-stake test still graded 10 - the top rating - with a rot index of zero after ten years. Utility poles, marine pilings, retaining timber and pergola posts fall squarely in this class.

The actives are a stable copper-ammonia complex plus a quaternary ammonium (DDAC): 15% total actives expressed as copper-oxide equivalent, roughly CuO 10% + DDAC 5%, in a deep-blue liquid at pH 9.0–10.5. As the ammonia flashes off, copper fixes out as basic copper carbonate while the quat supplies added fungicidal and termite activity. ASTM D-1627 shows a fixation rate above 85% in the wood, and the product is EPA-registered with no arsenic, chromium or phenols.

Against house termites under AWPA E7 the mass loss runs under 3%. Under the AWPA E11 leaching test loss is under 20%, qualifying the charge for ground contact and fresh-water immersion, and the formulation meets AWPA UC4 severe-decay use. A field check on a Fujian boardwalk a decade after treatment found no decay and no termite damage. Corrosion of galvanised steel drops about 30% versus CCA, though stainless or hot-dip fixings are still recommended.