The role of boron-based additives in exterior wood coatings

Conclusion

Borates are clearly multi-functional coatings additives in the truest sense. Wood coatings can benefit from the biostatic, tannin stain resistance and flame retardant properties of borates. In addition, protection in storage is carried over into service and consequently borates can offer extremely cost effective solutions for the production of high performance coatings. Just one example, if zinc borate were being used for tannin stain resistance, it is unnecessary to use a separate dry film fungicide, in-can preservative or in-can corrosion inhibitor.

Coupled with the fact that borates have diverse physical characteristics, in particular distinct aqueous solubilities and pH characteristics (anywhere between pH 4 and 11), it is possible to match the formulation environment and avoid incompatibility and stability problems. Other useful characteristics include their low effect on the optical properties of the dry paint film and, unlike certain organic additives, zinc borate will not alter the transmission properties of transparent coatings; so important at a time when semi-transparent woodstains are gaining popularity.

Increasingly the coatings industry is being limited in the additives it can use; either because of specific product restrictions, a general trend to water-borne technology or because of rising raw material costs. It can be concluded from data reviewed here that the borates offer an environmentally non-harmful, safe and cost-effective alternative to the coatings formulator.