Exposure testing of fasteners in preservative treated wood: Gravimetric corrosion rates and corrosion product analyses

Research was conducted to determine the corrosion rates of metals in preservative treated wood and also understand the mechanism of metal corrosion in treated wood. Steel and hot-dip galvanized steel fasteners were embedded in wood treated with one of six preservative treatments and exposed to 27 °C at 100% relative humidity for 1 year. The corrosion rate was determined gravimetrically and the corrosion products were analyzed with scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Although the accepted mechanism of corrosion in treated wood involves the reduction of cupric ions from the wood preservative, no reduced copper was found on the corrosion surfaces. The galvanized corrosion products contained sulfates, whereas the steel corrosion products consisted of iron oxides and hydroxides. The possible implications and limitations of this research on fasteners used in building applications are discussed.

Research highlights
► The composition of the corrosion products was similar for the nail head and shank.
► Reduced copper was not detected on any of the fasteners.
► Measured corrosion rates were between 1 and 35 μm year−1.