Effect of grain size and crystallographic orientation on the corrosion behaviors of low alloy steel

In this work, low alloy steels with different grain size and crystallographic orientations were prepared by advanced thermo-mechanical processes, and the microstructure and electrochemical corrosion behaviors were characterized by electron backscatter diffraction (EBSD), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. Results indicated that grain refinement decreased corrosion resistance in NaCl solution but improved corrosion resistance in NaHCO₃ solution. As distinguished from coarse-grained steels with anodic passivation, grain refinement can induce self-passivation. Moreover, the existence of texture would result in the anisotropic corrosion behavior of low alloy steels. This work would help to understand the contradiction in existing literature about the effect of grain refinement on corrosion behaviors and the effect of microstructure on corrosion behavior in an active and passive system.