Characterisation of rust formed on carbon steel after exposure to open atmosphere in Qinghai salt lake region

The rust layer formed on carbon steel after 1 year exposure to Qinghai salt lake atmosphere was characterised by the following complementary techniques: X-ray diffraction, infrared transmission spectroscopy, scanning electron microscopy and energy dispersive X-ray. The crystalline components of the rust layers consisted primarily of β-FeOOH, γ-FeOOH and iowaite [Mg4Fe(OH)8OCl.4H2O]. δ-FeOOH, ferrihydrite and amorphous rust were also found. Most corrosion products were contained in the inner layer, while foreign particles were mainly distributed in the outer layer. Energy dispersive X-ray and linear scanning results indicated that Cl and Mg elements were rich in the whole rust layer, in which case they will have had an important influence on the corrosion process of carbon steel in the salt lake atmospheric conditions.