Corrosion behavior of as-cast Al0.75CoFeCr1.25Ni high entropy alloy in 0.5 mol/L NaOH solution

The corrosion behavior of an Al0.75CoFeCr1.25Ni high-entropy alloy (HEA) in 0.5 mol/L NaOH solution was investigated using a series of electrochemical and analytical techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, potentiodynamic polarization measurement and electrochemical impedance spectroscopy. The results showed that the Al0.75CoFeCr1.25Ni HEA exhibited a typical columnar dendritic structure, which is composed of face-centered cubic, body-centered cubic (BCC), and ordered BCC phases (B2 phase). The corrosion resistance of this HEA in 0.5 mol/L NaOH solution is comparable to that of 304 SS, attributed to the change in the composition of the passive film formed on the surface. Although the passive film formed was generally rich in Al, the proportion of Cr2O3 inside it increased with the increasing immersion time, enhancing the stability of the passive film and thus improving the corrosion performance of this HEA in 0.5 mol/L NaOH solution.