Microstructure and Intergranular Corrosion Sensibility of FeCoNiCrMn High Entropy Alloy

In the present study, a high-entropy alloy (HEA) composed of iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), and manganese (Mn) was fabricated in its as-cast state. Microscopic examination revealed the presence of prominent dendritic segregation within the HEA microstructure. The electrochemical response of the HEA was evaluated using anodic polarization curves. These curves indicated active dissolution behavior in 0.5 M hydrochloric acid (HCl) solution, active–passive behavior in 0.5 M sulfuric acid (H₂SO₄) solution, and immediate passivation in 0.5 M nitric acid (HNO₃) solution. Notably, the HEA exhibited the most positive corrosion potential and the lowest corrosion current density in the HNO₃ solution. Post-polarization analysis revealed the most severe instance of intergranular corrosion within the HEA exposed to the HCl solution. Conversely, immersion corrosion testing demonstrated the highest susceptibility to intergranular corrosion in the HNO₃ solution, followed by the HCl solution, with the least susceptibility observed in the H₂SO₄ solution. The underlying mechanisms responsible for these corrosion behaviors were elucidated using mixed potential theory.