”X-ray Analysis on the Atmospheric Corrosion Products in Commercial Low and Medium Carbon Steels.”

Major components of the atmospheric corrosion products are analyzed on SS 41 both as bright finished and as hot rolled conditions and on S55C as hot rolled condition, and they are found to be four different corrosion products of α-Form FeOOH, γ-Form FeOOH, FeSO_4 and Fe_3O_4. The former three of them have an orthorhombic crystal structure and the last one a face centered cubic structure. Variations in X-ray intensities and relative volume of these corrosion products are shown to be functions of the exposed time in the air. The stable product of α-Form FeOOH increases in its relative amount with an increase in the exposed time and the comparatively unstable one of γ-Form FeOOH shows rather a decrease in its relative amount in the long exposed time of 480 days. The formation of FeSO_4 seems to follow the parabolic corrosion law of α=Kt^n. The intermediate stage oxide of Fe_3O_4 shows a little increase in its relative volume with the elapsed time and no evidence of being FeO has been examined. The dependence of each corrosion product on the concentration of SO_3 in the air is also reported.