Influences of Fe ₃C and pearlite on the electrochemical corrosion behaviors of low carbon ferrite steel

The microstructure of X80 pipeline steel welding joint, consisted of Fe ₃C and degenerated pearlite, was simulated by carburizing treatment. The effects of Fe ₃C and pearlite on the electrochemical properties of bainitic ferrite steel and localized corrosion occurrence regularity in Yingtan soil simulation solution were investigated by scanning Kelvin probe (SKP), scanning vibrating probe (SVP) and local electrochemical impedance spectroscopy (LEIS), combined with immersion test. It is demonstrated that the corrosion potential of degenerated pearlite is lower than bainitic ferrite, and decreases with increasing Fe ₃C content. Localized corrosion occurs on the surface of the carburized sample in Yingtan soil simulation solution. The anodic oxidation process is observed to be initiated on the carburized degenerated pearlite, whereas the cathodic reaction involving dissolved H ⁺ is on bainitic ferrite, and the anodic current density increases with increasing Fe ₃C concentration. As the ion contents of the soil simulation solution doubled, the anodic dissolution of degenerated pearlite increases, and the local impedance of the electrode decreases.