Effects of Proton Irradiation and Chloride Ions on the Corrosion Behavior of Stainless Steel 304L

Non-irradiated and proton-irradiated stainless steel (SS) 304L samples were subjected to corrosion tests in various concentrations of Cl⁻ ions at room temperature. The electrochemical impedance spectroscopy techniques were used to investigate the corrosion behavior, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the phase composition and surface morphology. After irradiation, the open circuit potential (OCP) of SS 304L shifted from the passive state to the active dissolution state. It caused the shift of the anodic current peak towards the lower potential, demonstrating the reactivity of the surface and it may increase the corrosion process. The lower semi-circle of impedance for the irradiated SS 304L confirms the localized corrosion process and breakdown of passive films, it enhanced the localized corrosion as indicated by SEM. XRD peak shows a slight shift in the negative direction and formation of Fe₃O₄, for irradiated SS 304L samples. The surface morphology of the irradiated sample consisted of tiny pieces of corrosion product in the surroundings of pits. In contrast, the number and size of pits increased with the concentration of Cl⁻ ions in the solutions. Higher Cl⁻ ions are aggressive towards pitting corrosion for the non-irradiated SS 304L, however, irradiation accelerated the pitting initiation process for SS 304L.