Corrosion behavior of Hf0.5Nb0.5Ta0.5Ti1.5Zr refractory high-entropy in aqueous chloride solutions

The Hf0.5Nb0.5Ta0.5Ti1.5Zr refractory high-entropy alloy with excellent corrosion resistance in the 3.5 wt% NaCl solution is identified in this work. This refractory high-entropy alloy exhibits much better general corrosion resistance than that of the 316L stainless steel, due to its corrosion current density being about one fifth of that in the latter. Meanwhile, the pitting potential of Hf0.5Nb0.5Ta0.5Ti1.5Zr reaches an unusually high value of +8.36 V, much higher than that of reported high-entropy alloys. The superior passivity of Hf0.5Nb0.5Ta0.5Ti1.5Zr is accredited to the formation of a single-phase solid solution containing high amount of homogenously distributed passivity-promoting elements, and also the existence of metallic Ta and OH− species in the passive film, which contribute to the high immunity to passive film breakdown. •Hf0.5Nb0.5Ta0.5Ti1.5Zr contains finely distributed passivity-promoting elements.•Hf0.5Nb0.5Ta0.5Ti1.5Zr exhibits better general corrosion resistance than 316L SS.•Epit of Hf0.5Nb0.5Ta0.5Ti1.5Zr reaches +8.36 V, beating all other reported RHEAs.