INITIAL ATMOSPHERIC CORROSION OF A3 STEEL IN THEPRESENCE OF NaCl AND SO2

摘要

Atmospheric corrosion of A3 steel in the presence of NaCl and SO2 was investigated at 25℃rnand 80%RH in laboratory. Regularity of the initial atmospheric corrosion of A3 steel under thesernconditions was analyzed. The results show that NaCl can accelerate the corrosion of A3 steel. Mass lossrnof A3 steel increases with the exposure time, which can be correlated by the law of the type ?m/A=Kt n.rnThe relationship between mass loss and amount of NaCl deposition follows the quadratic function both inrnSO2-free air and in air containing 1 ppm SO2. The combined effect of NaCl and SO2 on the corrosion ofrnA3 steel is greater than that caused by each single component. X – ray diffraction (XRD), FourierrnTransform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) combined with energyrndispersive X-ray analysis (EDAX) were used to characterize the corrosion products of A3 steel. In thernabsence of SO2, α -FeOOH, β -FeOOH, γ -FeOOH, Fe3O4 and γ -Fe2O3 are the dominant corrosion products,rnwhile β -FeOOH, γ -FeOOH, Fe3O4 and FeSO4 ?H2O dominate in the presence of SO2. Brief discussion onrnthe mechanisms of atmospheric corrosion under these conditions was introduced.