Corrosion of metals in wood
In the past, gravimetric corrosion data for fasteners exposed to treated wood has been reported as a percent weight loss. Although percent weight loss is a valid measure of corrosion for comparing identical fasteners, it can distort the corrosion performance of fasteners with different geometries and densities. Previously, the authors developed a method for measuring the surface area of threaded fasteners, which now allows corrosion rates to be calculated. This work reevaluated a key report on the corrosiveness of wood treated with chromated copper arsenate (CCA) and ammoniacal copper arsenate (ACA) and converted the historical data into corrosion rates. In addition, similar experiments were run in wood treated with alkaline copper quaternary (ACQ). Comparison of the corrosion rates revealed that ACQ treated wood is more corrosive than CCA treated wood for all metals. This research has life-safety implications because most decks in the United States are built with treated lumber and fastened with metal connections, which corrode over time. This research gives engineers corrosion rates that can be used to calculate how rapidly fasteners will corrode in wood structures; prior to this, the actual rates were unknown.