Corrosion mechanism of eutectic high-entropy alloy induced by micro-galvanic corrosion in sulfuric acid solution

The corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) in aerated 0.5 M H2SO4 solution was investigated. The initial and long-term corrosion of EHEA were respectively controlled by the micro-galvanic corrosion cells established between Cr-rich FCC (cathode) and Al-rich/Cr-depleted BCC (anode) phases and between the lamellar (anode) and irregular (cathode) regions. Correspondingly, the main corrosion type of EHEA transformed from the preferential dissolution of BCC phase to the predominant localized corrosion of the whole lamellar region. EHEA exhibited electrochemical passivation property comparable to 304 L stainless steel and superior corrosion resistance relative to most Al-containing dual-phase HEAs.