Carbon and low-alloy steels are considered resistant only to very mild corrosives, while the various high-alloy grades are applicable for varying situations from mild to severe services, depending on the particular conditions involved. This article describes the factors that must be considered, by alloy casting users, in material selection. It presents compositions of cast steels tested in atmospheric corrosion in a tabular form. The rate of corrosion of a material in an environment can generally be estimated with confidence only from long-term tests. The article graphically presents the results of a research program that compared the corrosion resistance of nine cast steels in marine and industrial atmospheres. It illustrates the comparison of corrosion rates of cast steels, malleable cast iron, and wrought steel after 3 years of exposure in two atmospheres and provides the conclusions drawn from these tests.