Study of the corrosion behavior of an intermetallic Fe–Al–Ni alloy in acid solutions

The corrosion behavior of a cast Fe–Al–Ni-based alloy with Ag was assessed using electrochemical techniques. The Fe–Al–Ni alloy was produced by casting in a vacuum induction furnace, and corrosion measurements were conducted using a three-electrode cell in solutions with pH values of 4, 6, and 8. Results showed that the alloy's microstructure included a minor Ag₃Al phase, homogeneously dispersed within the β − (Fe,Ni)Al phase. Corrosion measurements indicated the highest current density and corrosion rate at pH 6, with lower current density at pH 8. Uniform corrosion with a passive layer formed by Al(OH)₃ was observed. Corrosion rates were generally below 0.19 µm/year, with a minimum of 0.05 µm/year at pH 8. The influence of solution pH and measured cell potential on the corrosion resistance of the Fe–Al–Ni + Ag alloy was correlated with the potential-pH phase diagrams for Al, Fe, and Ni in water. Based on its performance, this alloy appears suitable for petrochemical and subsoil applications.