DE-13-039 -- Corrosion of Embedded Metals in Wood: An Overview of Recent Research with Implications for Building Moisture Design PDF

Standard 160, Criteria for Moisture-Control Design Analysis in Buildings, specifies moisture design criteria in buildings to prevent moisture damage such as fungal activity and corrosion. While there has been much research on mold and decay fungi in wood buildings, it is often overlooked that wet wood is corrosive to the metal screws or nails used to fasten it. Currently, corrosion design in Standard 160 is based upon relative humidity criteria that were developed for atmospheric corrosion. However, the corrosion of metals embedded with wood is controlled by wood chemistry and moisture content rather than atmospheric relative humidity. This paper highlights recent research on the corrosion of metals in wood that may be of interest to those in the building moisture design community who develop codes, standards, and hygrothermal models to minimize the results of structure problems caused by fastener corrosion. The major design implications are that (1) corrosion of metals in wood is not the same as atmospheric corrosion, and (2) that the wood moisture content should be kept below 18%.