Corrosion Properties of Cu-P Bearing Low Alloy Steels Exposed to the Saline Environments with the Cyclic Variation between Wet and Dry

Paid particular attention to the characteristics of rust layers, this study was conducted to research the corrosion behavior of low-alloy steel containing small amounts of Cu and P in the saline environment which composes cyclic variation between wet and dry periods. Corrosion resistance of the low-alloy steel depends on the relative humidity of atmosphere in dry periods. According to the results of the X-ray diffraction analysis of rust layers and polarization measurements, cathodic reaction of the low-alloy steel exposed to this environment is reduction of β and γ FeOOH to Fe3O4. EPMA analysis of rust layers indicates that localized corrosion of low-alloy steel proceeds in chloride nest to which chloride ions are concentrated. The tight rust layer containing Cu acts as effective barrier to the permeation of chloride ions.