Corrosion avoidance with new wood preservatives

Abstract

The increased use of alkaline copper quaternary (ACQ) and copper azole (CuAz) as wood preservatives for residential construction has led to concerns about the corrosion performance of fasteners. Information on the effects of these preservatives on the corrosion rate is limited, although Simpson Strong Tie has published a technical bulletin indicating that both ACQ and CuAz are roughly twice as corrosive as chromated copper arsenate (CCA) and recommends fastener types for a given environment and preservative (Simpson Strong Tie 2005). It is believed that ACQ and CuAz are more corrosive than CCA due to the higher percentage of copper in these preservatives and absence of chromium and arsenic; both are known as corrosion inhibitors. While accelerated tests exist for estimating the corrosiveness of new wood preservatives currently, there is no way to relate the results of these tests to in-service performance. For information about the effect of new wood preservatives on corrosion, and a critical review of test methods used to measure corrosion in wood, see Zelinka and Rammer (2005). Currently, many products are marketed for use with new wood preservatives, in lieu of using stainless steel connectors or fasteners. With so many “corrosion-resistant” alternative products on the market, it is important to know the fundamental principles of corrosion protection to make informed decisions when designing structures. This article focuses on considerations that need to be made when choosing products, other than stainless steel, to minimize corrosion of metals in contact with treated wood.

Citation

Zelinka, Samuel L.; Rammer, Douglas R. 2006. Corrosion avoidance with new wood preservatives. Wood design focus. Vol. 16, no. 2 (summer 2006): pages 7-8.