Corrosion resistant nanostructured eutectic high entropy alloy

•A nanostructured eutectic high-entropy alloy (EHEA) with composition of FeCrNiCoNb0.5 was developed.•The EHEA shows superior corrosion-preventive and repassivation ability in 1 M NaCl.•Amorphous passive film formed on EHEA is compact and protective.•The unique nanostructure effectively prohibited pitting corrosion. In this work, we developed a nanostructured eutectic high entropy alloy (EHEA) of composition FeCrNiCoNb0.5 (atomic %). Due to the formation of a compact amorphous high entropy passive film and the two-phase nanostructure, our EHEA exhibits unique combination of a low corrosion current density, a large passivation region and a superior repassivation ability in 1 M NaCl, outperforming the variety of conventional alloys and other high entropy alloys hitherto reported. The outcome of our research suggests that the notion of EHEAs could be explored to design corrosion resistant chemically complex alloys.