Atmospheric Corrosion Resistance of Skyward- and Groundward-Exposed Surfaces of Zinc- and 55% Al-Zn Alloy-Coated Steel Sheet

Zinc-coated (galvanized) and 55% Al-Zn alloy-coated steel sheet was tested for atmospheric corrosion resistance for 20 years in rural (Saylorsburg, Pennsylvania), industrial (Bethlehem, Pennsylvania), moderate marine (250-m [880-ft] lot, Kure Beach, North Carolina), and severe marine (25-m [80-ft] lot, Kure Beach, North Carolina) environments. Corrosion losses were determined separately for skyward- and groundward-exposed surfaces and compared to results for conventional two-sided coupons, which gave only an average of skyward and groundward surfaces. Results were fitted to exponential equations of the form C = AT(B), where C is the corrosion loss, T is time, and A and B are constants. Coating lives were estimated based upon extrapolation of these equations to the time to reach a corrosion loss equal to the coating thickness. On average, the estimated life of a skyward-exposed 55% Al-Zn alloy coating was 12 times that of a galvanized coating of equal thickness (25 mm). Editor's Note: Originally published in Corrosion 54, 7 (1998): p. 561-565. When citing "Atmospheric Corrosion Resistance of Skyward- and Groundward-Exposed Surfaces of Zinc- and 55% Al-Zn Alloy-Coated Steel Sheet," please cite the original version.