Atmospheric corrosion of different steels in marine, rural and industrial environments

The atmospheric corrosion of the different steels at the different exposure conditions has been investigated by Mössbauer and Raman spectroscopies and XRD. Goethite and lepidocrocite were identified in the corrosion products formed on all the coupons. Magnetic maghemite, which resulted in the high corrosion rate, formed on the carbon steel exposed at the marine site. The inner layer, a protective layer, mainly consisted of interdispersed goethite, and the outer layer mainly composed of interdispersed lepidocrocite. The larger fraction of superparamagnetic goethite, which resulted in decreasing the mean particle size of goethite, in the corrosion products was closely related to reduction in the corrosion rate in the marine and rural sites. The larger amounts of silicon and smaller amounts of phosphorus in the steel increased the fraction of superparamagnetic goethite. However, different amounts of nickel did not affect the formation of the iron oxides after sixteen years of exposure.