Study on rust layers of carbon steel, weathering steel and alloy steel exposed to Shanghai atmosphere for three years

The corrosion results of four steels (including carbon steel, weathering steels and alloy steel) exposed to atmospheric environment in Baoshan District of Shanghai for three years were systematically analyzed by means of corrosion weight loss, intelligent digital microscope, scanning electron microscope, energy dispersive spectrometer, confocal microscopy Raman spectrometer, etc. The rust layers on skyward surfaces of corrosion samples were characterized. The results showed that the atmospheric corrosion rate of carbon steel was the highest, and the rust layer exfoliated more. The rust layers of weathering steels and alloy steel exfoliated less, and Cr was enriched in the inner layers, which promoted the formation of compact and protective rust layers, prevented rust exfoliation and oxygen infiltration, contributed to crack restoration, and thus improved atmospheric corrosion resistance.