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

The corrosion behavior of AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) in aerated 0.5 M H 2 SO 4 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. • The corrosion behavior of EHEA in aerated 0.5 M H 2 SO 4 solution was studied. • Micro-galvanic corrosion remarkably affected the corrosion process of EHEA. • Micro-galvanic corrosion between FCC and BCC phases for short-term corrosion. • Micro-galvanic corrosion between lamellar and irregular regions for long-term. • Predominant dissolution of EHEA changed from BCC phase to whole lamellar region.