Environmental effects on materials Effect of SO2 on the corrosion of unalloyed steel and weathering steel – an attempt to simulate Atmospheric Corrosion

Laboratory exposures of unalloyed steel and weathering steel have been performed in humid atmospheres and atmospheres containing sulphur dioxide in order to simulate atmospheric corrosion. No significant difference in the corrosion mechanism of the two steels was observed. At high sulphur dioxide concentrations (10 ppm) a large amount of iron sulphates was formed resulting in an unrealistic corrosion behaviour compared to atmospheric corrosion, while at lower concentrations (0.5 ppm) a more realistic behaviour was observed. The microstructures of the corroded surfaces were investigated by scanning electron microscopy (SEM/EDX). Corrosion products were analysed using X‐ray diffraction (XRD) and ion chromatography (IC). Results from gravimetric evaluation are also reported.