Roles of grain refinement in the rust formation and corrosion resistance of weathering steels

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Weathering steels with different grain sizes (20.0 µm, 3.8 µm, and 0.6 µm) were prepared through a combination of cold-rolling and heat-treatment processes. Their corrosion behaviors were investigated using wet/dry cyclic corrosion tests in 3.5 wt% NaCl solution. The results indicate that grain refinement has a positive effect on the rust layer formation. It accelerates the formation of a more stable, compact, and protective rust layer, along with enhanced enrichment of alloying elements (Cr, Ni, and Cu) as oxide compounds within the rust layer. Moreover, grain refinement shows promise in inhibiting non-uniform corrosion and the formation of "deep-and-narrow" corrosion pits.