Understanding of the Interaction Between Crystallographic Orientation and Service Environment on Nonoriented Silicon Steel Corrosion

The effect of crystallographic orientation and environmental factors on the corrosion behavior of 35TWV1900 nonoriented silicon steel at various temperatures (25°C, 40°C, and 60°C) and Cl⁻ concentrations (0.1 mol/L, 0.6 mol/L, and 1 mol/L) were investigated by electrochemical tests and immersion experiments. The results have revealed that the (111) plane exhibits a higher corrosion rate compared with (001) and (101) planes. The increased temperature promotes the anodic dissolution of the substrate, accelerating the formation of corrosion products and the transformation of β/γ-FeOOH to α-FeOOH/Fe₃O₄. In the immersion environment, the corrosion mechanism is a typical oxygen-absorbing corrosion mechanism. During the electrochemical reaction phase, the corrosion rate shows a trend of first increasing and then decreasing with the increase of Cl⁻ concentration, which can be explained by the catalytic dissolution effect and the protective effect of adsorbed Cl⁻ on the surface. Meanwhile, with the injection of Cl⁻, the content of dissolved oxygen in the solution decreases and the adsorption competition between Cl⁻ and oxygen increases, leading to the reduction of corrosion rate and inhibiting the formation of an oxide film. The two stages of corrosion in an immersion environment are described, and the corrosion mechanism is elucidated.