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

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 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 high-entropy alloy (HEA), and systematically investigated its corrosion behavior and passive film evolution in boiling HNO 3 solution compared with 321 stainless steel, thereby helping to elucidate the corrosion resistance mechanism of this HEA. Experimental results indicate that the AlCo 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 HEA consists of BCC, B2, and σ phases. In boiling HNO 3 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 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 HEA promotes surface oxidation through autocatalytic reduction in boiling HNO 3 , forming a hybrid passive film with Cr 2 O 3 as the matrix and Al 2 O 3 dispersed within it. This hybrid passive film structure demonstrates superior resistance to boiling HNO 3 corrosion compared to a single Cr 2 O 3 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.