Study on the corrosion behavior and mechanism of AlCo 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 high-entropy alloy in nitric acid solution

Abstract

The inherent limitations of traditional stainless steels, particularly the inhomogeneity and instability of their passive films, may increase their susceptibility to corrosion under severe conditions. To break through the performance limits of corrosion-resistant materials, this study employed high-vacuum cold crucible suspension melting technology to prepare AlCo_0.2Cr_1.7FeNi_2.1Mo_0.1 high-entropy alloy (HEA), and systematically investigated its corrosion behavior and passive film evolution in boiling HNO₃ solution compared with 321 stainless steel, thereby helping to elucidate the corrosion resistance mechanism of this HEA. Experimental results indicate that the AlCo_0.2Cr_1.7FeNi_2.1Mo_0.1 HEA consists of BCC, B2, and σ phases. In boiling HNO₃ solution, its corrosion rate is significantly lower than that of 321 stainless steel, and this performance gap further widens over time. XPS results confirm that the AlCo_0.2Cr_1.7FeNi_2.1Mo_0.1 HEA promotes surface oxidation through autocatalytic reduction in boiling HNO₃, forming a hybrid passive film with Cr₂O₃ as the matrix and Al₂O₃ dispersed within it. This hybrid passive film structure demonstrates superior resistance to boiling HNO₃ corrosion compared to a single Cr₂O₃ film. This study provides insights that extend beyond the corrosion resistance typically achieved by conventional materials by constructing a multi-component hybrid passive film and provides a highly promising candidate material for extreme environments such as nuclear fuel reprocessing.