Corrosion characteristics of low-carbon steel in hot and humid industrial-marine atmosphere

The corrosion behavior of low-carbon steel was investigated in a simulated hot and humid industrial-marine atmosphere by X-ray powder diffraction (XRD), scanning electron microscopy with X-ray microanalysis (SEM-EDS), mass loss, and a wet/dry alternate immersion corrosion test using a 0.1 mol·L^-1 NaCl+0.01 mol·L^-1 NaHSO₃ solution. The results indicate that the corrosion processes of the experimental steels agree well with the d=Atⁿ power function, with different steels having different values of A and n. The corrosion products are mainly in the amorphous phase and contain a small amount of Fe₃O₄, α-FeOOH, β-FeOOH, and γ-FeOOH crystals. It can be found that the rust layers have two parts-the body of the rust layer and a loose interface band. The Fe and O content gradients in the rust layer, from inner to outer, change very little. It can be concluded that the long-term interaction of Cl^-, SO₂ and H₂O will lead to the deterioration of the inner structure. However, the addition of elements with high stability or corrosion resistance can improve the stability and density of the rust layer, and thereby enhance the corrosion resistance of the steels.