Influence of Composition and Thickness on the Atmospheric Corrosion of Steel and Zinc and the Implications for Standards, Specifically ISO 9226

The influence of composition on the atmospheric corrosion rate of steel and zinc was studied with specific reference to the copper content. It was found that the composition limits for steel and zinc in the International Organization for Standardization (ISO) Standard 9226 are inadequate to ensure that the materials will give a reproducible batch-to-batch performance, and that as a consequence, the specifications for these materials will not enable them to serve as absolute standards. The problem exists for zinc only in ASTM Standard G92. Recommendations are made that a copper-bearing structural carbon steel (with 0.2% Cu minimum) be used for characterizing steel corrosivity and that the thickness of standard corrosion specimens be specified separately for steel and zinc. The issue of season/start times of exposure on the ultimate corrosion rate of zinc also is discussed.