Corrosion behavior of low-alloy weathering steel in environment containing chloride ions

The corrosion behavior of two low-alloy weathering steels, A588 and SPA-H, in an environment containing chloride ions was investigated by alternate wet-dry accelerated corrosion tests. The effects of Ni and Mn elements on the corrosion behavior were studied by using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron microprobe analysis (EMPA). It is shown that the rust layer is mainly composed of Fe₃O₄, γ-FeOOH and α-FeOOH; however, their contents are somewhat different for the two experimental steels. The content of Ni in the inner rust layer is higher than that in the outer rust layer, and Mn is enriched at pores in the rust layer. The inner rust layer is more compact than the outer rust layer. The compactness of the inner rust layer is improved by increasing the Ni and Mn contents, thereby increasing the corrosion resistance of the low-alloy steel.