Wood preservation facilities, inorganic boron (borate): chapter I-1

1. Production and Use

Inorganic boron (borate) wood preservation chemicals are generally sold as disodium octaborate tetrahydrate, which is supplied as a water-soluble inorganic borate salt (powder) with insecticidal, termiticidal and fungicidal properties. Treating solutions are stored in mild steel (carbon steel) tanks and are applied to wood under pressure until a predetermined amount has been absorbed by the wood in accordance with applicable standards (1). On removal of the wood from the pressure vessel, treated wood is stored in a roofed area or under wrap. It remains wrapped at all times until final use. It should be noted that borates are water soluble, and treated wood is suitable only for applications where the wood is not in contact with the ground and is continuously protected from free water.

Although borates have been used for over 50 years by diffusion processes for interior applications, it is now mostly applied pressure treatment in North America for lumber and timber for interior construction. Currently there are two impregnation plants operating in Canada that use borates (2). Table 1 presents basic information on use of borates in Canada.

The CSA O80 Series of Standards specifies requirements related to the preservation and fire retardance of wood through chemical treatment (pressure), which includes Boron-treated products. (1)

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