Abstract: The corrosion resistance of Fe Co Ni Cr Mn high-entropy alloy and low-carbon stainless steel weld materials in nuclear fuel reprocessing pipeline environments were systematically investigated through electrochemical testing,XPS analysis,and immersion corrosion experiments. Electrochemical tests indicated that in a 2 mol/L HNO₃ solution,the corrosion current density of the high-entropy alloy was reduced by approximately 50% compared to that of the stainless steel,with a significant enhancement in the stability of the passivation film. XPS analysis revealed that the total content of Cr element in the passivation film of the high-entropy alloy reached atomic fraction of 40%,forming a dense passivation layer centered on Cr₂O₃. In contrast,the passivation film of the stainless steel was predominantly composed of Fe-based oxides with atomic fraction of higher than 35%. Combining immersion corrosion experiments with polarization curve analysis,it was found that the high-entropy alloy,through a "high-Cr/low-Fe" compositional design strategy,effectively blocked the penetration of corrosive media via the chemical inertness of Cr₂O₃ in the passivation film. Meanwhile,the synergistic effect of Ni and Co oxides effectively reduced the density of point defects. This study elucidated the corrosion resistance mechanism of high-entropy alloy and low-carbon stainless steel from the perspective of the relationship between film composition,structure,and properties,providing a theoretical basis for their engineering applications in nuclear chemical equipment.