Copper-Based Systems for Exterior Residential Applications

Environmental concerns and health issues related to the use of arsenic- and chromium-containing preservatives for residential applications have prompted the use of copper-based systems which typically contain copper(II) with an organic co-biocide added to control copper-tolerant fungi for exterior residential applications. This chapter deals with copper-based systems that contain no other metals. Copper-based systems include ammoniacal, alkaline and amine copper quat (ACQ types B, C and D), copper azoles (CBA and CA-type B), oxine copper (Cu-8), copper HDO, oilborne and water dispersible copper naphthenate, copper dimethyl dithiocarbamate (CDDC), copper borate and copper citrate (CC). The retention level, penetration, corrosiveness and leaching of copper from treated wood varies with the formulation of the treating solution, which is dependent on the form of copper (sulfate, nitrate, hydroxides, carbonates, metal), the amine/ammonia to copper ratio, the addition of corrosion inhibitors, the pH of the formulation and the inactive ingredients. The copper level generally required for residential above ground and ground contact applications is about 1.5 Kg.m(-3) and 2.5 kg.m(-3), respectively, but much less copper is necessary with the organometallics Cu-8 and copper naphthenate.