Wood preservation facilities, ammoniacal copper zinc arsenate: chapter C-1

1. Production and Use

Ammoniacal copper zinc arsenate (ACZA) is a water-borne formulation that can be purchased in a premixed solution only. It use to be prepared on-site at wood preservation facilities by mixing and oxidizing arsenic acid, copper oxide, zinc oxide, ammonium hydroxide, ammonium bicarbonate and water.

ACZA is bought as a concentrate; 9.92% total oxide as CuO, ZnO and As₂O₅ at an approximated ratio of 2:1:1. For the preparation of work solutions (0.5% to 10% active ingredients) the concentrate is diluted with requisite amounts of water. Totes rinsate and effluent water can be used for this purpose. The use of Ammonium Hydroxide concentrate can sometime be use to top up the ACZA concentrate if the ammonia levels gets low.

ACZA is particularly suited for treatment of refractory wood species such as Douglas Fir. Major products are construction timbers (e.g. highway timbers), fence posts and marine structures. ACZA uses for such industrial applications are summarized in Table 1

Although ACZA was developed in Canada and has been used in the United States for about twenty years, it was not introduced commercially into Canada only until 1999.

ACZA treated wood was produced in Canada until 2006 (1). In 2012, no facility in Canada used ACZA preservative. However one facility is scheduled to begin treating operations with ACZA in 2013. (2).

The CSA O80 Series of Standards specifies requirements related to the preservation and fire retardance of wood through chemical treatment (pressure), which includes ACZA-treated products (3).

Treatment conditions must be calibrated to yield the target retention levels described on the pesticide label.