With the voluntary withdrawal of wood treated with chromated copper arsenate (CCA) for use in residential construction in January 2004, the corrosiveness of treated wood has become a concern. Preliminary research has shown the replacements for CCA, which include copper azole (CuAz) and alkaline copper quaternary (ACQ) are more corrosive than CCA. Since rapid tests cannot easily be run in solid wood, an electrochemical method has been developed that measures the corrosiveness of water-extracts of wood. Corrosion rates of steel and galvanized steel fasteners measured in the extract of ACQ treated wood correlate well with gravimetric data in solid wood.