Corrosion behavior and mechanism of dual phase Fe_1.125Ni_1.06CrAl high entropy alloy

This investigation explores the corrosion behavior and mechanism of as-cast dual phase Fe_1.125Ni_1.06CrAl high entropy alloy with low density (6.65 g/cm³) and high hardness (460.67 kgf/mm²) in 3.5 wt% NaCl solution. The microstructure, elemental distribution and corrosion behavior of high entropy alloys before and after the corrosion process were investigated via electrochemical quantitative analysis and then the corrosion mechanism of high entropy alloys was obtained by the first principles and experimental modeling approaches. The results show that quaternary Fe_1.125Ni_1.06CrAl high entropy alloy display spinodal decomposition microstructure of dual BCC phase with high hardness and distinguished corrosion resistance compared with other established alloys. The self-corrosion current density of 9.262 × 10⁻⁹ A/cm² and corrosion potential of − 0.228 V are gotten for this alloy via potentiodynamic polarization measurements and the calculated parameters of high entropy alloys were analyzed by fitting equivalent circuit. Corrosive pits emerged on the alloy surface when the Fe_1.125Ni_1.06CrAl and Fe_1.125Ni_1.125CrAl specimens have experienced preferentially localized corrosion at the areas enriched in Ni and Al characterized by scanning electronic microscope and atomic force microscope. Oxides and hydroxides films of constitutional elements on the alloy surface are formed by X-ray photoelectron spectroscopy analysis, which indicates that corrosion properties of high entropy alloys possess. Chloride anions are easier to be adsorbed and attacked on the BCC2 phase surface based on the adsorption behavior analysis, accelerating the localized pitting and micro-galvanic corrosion processes.