The effect of SO2, NO2, NO and O-3 on the corrosion of unalloyed carbon steel and weathering steel - The results of laboratory exposures

Laboratory exposures of unalloyed steel and weathering steel have been carried out in humid air containing Single air pollutants (SO2, NO2, NO, O-3 and laboratory air) in order to investigate their role in atmospheric corrosion. Realistic pollutant supply rates normally encountered in outdoor exposures were chosen for the experiments. Some experiments resulted in the formation of rust protrusions and corrosion products commonly formed during outdoor exposure. No significant difference in the corrosion behaviour of the two steels was observed. The effect of SO2 exceeds that of the other pollutants by far, but since ambient SO2-levels are considerably lower than those of NO2 and O-3, their effects in atmospheric degradation have to be taken into account as well. 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. Copyright (C) 1996 Elsevier Science Ltd.