In 1976, the ASTM G01.04 Subcommittee on Atmospheric Corrosion initiated a long-term atmospheric corrosion test program at five outdoor locations: Kure Beach, NC (25-meter East-coast marine), Newark-Kearney, NJ (industrial), State College, PA (rural), Point Reyes, CA (West-coast marine), and Fort Sherman, Panama (tropical marine). Among the forty-one materials exposed were four coated steel sheet products: G60 galvanized, G90 galvanized, 55% aluminum-zinc-coated, and Type 2 aluminum-coated. Results are presented for the performance of the coated sheet steels after 21 years. These results indicate the following qualitative order of corrosivity for five sites: Panama ~ Kure Beach > Newark-Kearny > State College > Point Reyes

Based on changes in the corrosion of 55% aluminum-zinc-coated, an increase in the aggressiveness at Panama took place sometime during the 10th to 21st year of exposure. Future testing at these sites could be better quantified by short-term (1–2 years) exposures of standard materials. A loss of significant data from 2-, 5- and 10-year removals and initial weights for many of the test materials highlights the importance of safeguards to ensure the integrity of future long-term ASTM tests.

In terms of relative performance, the results are consistent with the following order of corrosion resistance (most-to-least). T2 100 ~ AZ55 > G90 > G60