Summary of a ten year report produced by NAHB Research Center, a subsidiary of the National Association of Home Builders (NAHB) in the US and sponsored by International Zinc Association
Durability of Galvanized Steel Framing in Residential Buildings was a study commissioned by the International Zinc Association (IZA) that measured actual zinc and zinc-alloy coating corrosion rates of steel framing samples in four different home environments in the US and Canada over a ten year period. The NAHB Research Center was the research contractor
说是NAHB承包了这项研究，在美国和加拿大进行了一个TEN YEAR PERIOD关于镀锌和镀锌合金腐蚀的研究
This summary report is based on the corrosion data presented in the NAHB Research Center’s ten year sample retrieval report, January, 2009. The test sites were in Miami, Florida; Leonardtown, Maryland; and Long Beach Island, New Jersey in the US; and Hamilton, Ontario in Canada. At each site, numerous test samples were installed inside and in some cases, outside of the building (e.g.; roof trusses, floor systems, walls, decks). The ten year coating loss measurements from the four sites have shown minor mass losses for all coating types in all sample colonies (e.g., walls, attics, floor joists). While calculating life expectancies based on the very low coating weight losses found in this study is inexact, the measured coating corrosion rates extrapolate to coating life predictions of 300 to over 1000 years in wall, floor, and roof framing. Sample colonies intentionally located in more aggressive exposures, suchas underneath an outdoor deck and in an exposed crawl space located next to aggressive tidal waters, exhibited higher corrosion rates, but still had a coating life greater than 150 years. Steel is not recommended for outdoor use such as under decks. For an area near the coast or other aggressive bodies of water, steel in a vented or exposed crawl space would be specified with a heavier coating to significantly extend its life.
Coating corrosion was minimal from all four sites, for all sample types (studs and plates), all sample coatings (galvanize, Galvalume®, and Galfan®), and all sample colonies (e.g., crawl spaces, walls, attics, joists). Lower corrosion rates were found with samples installed in wall cavities and attics where the environments were more controlled with less exposure to humid conditions. Higher coating corrosion rates were found in locations with exposures to higher levels of humidity and outdoor pollutants, such as with samples installed in the floor above the carport of the New Jersey site or samples located in the crawl space of the Leonardtown site.For enclosed locations (walls, attics, floors) the extrapolated coating life predictions ranged from 300 to over 1000 years. For exterior exposures or semi-exposed locations in an aggressive environment subject to higher humidity and exterior pollutants, thehigher corrosion rates still extrapolated to over 150 years of coating life.The life span of the zinc and zinc-alloy coated steel samples studied in this project was found tobe well beyond the life expectancies of modern buildings. The results of this study agree with the results from a similar study conducted by Corus Research in the United Kingdom.