Dynamic Polarization Behaviors of Equimolar CoCrFeNi High-Entropy Alloy Compared with 304 Stainless Steel in 0.5 M H<sub>2</sub>SO<sub>4</sub> Aerated Aqueous Solution
Chao-Chun Yen,
Ting-Lun Tsai,
Bo-Wei Wu,
Yu-Chieh Lo,
Ming-Hung Tsai,
Shiow-Kang Yen
Affiliations
Chao-Chun Yen
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Ting-Lun Tsai
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Bo-Wei Wu
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Yu-Chieh Lo
Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
Ming-Hung Tsai
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Shiow-Kang Yen
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
Three corrosion potentials and three corrosion current densities are clearly identified before the passivation for both dynamic polarization curves of equimolar CoCrFeNi high-entropy alloy (HEA) and 304 stainless steel (304SS) in 0.5 M H2SO4 aerated aqueous solution, by decomposing anodic and cathodic polarization curves. The passivated current density of the former is greater than the latter, compliant with not only the constant of solubility product (ksp) and redox equilibrium potential (Eeq) of each metal hydroxide but also the sequence of bond energy (Eb) for monolayer hydroxide on their facets derived from the first principle founded on density function theory. However, the total amount of ion releasing from HEA is less than 304SS, since the hydroxide/oxide film formed in the air of the latter containing greater amounts of Fe(Ⅱ) and Mn(Ⅱ) is less stable around corrosion potentials while they are further oxidized into more stable Fe(Ⅲ) and Mn(ⅢorⅣ) with much lower ksp, leading to the much less increasing ratios of ion releases from 0.25 to 0.6 V.
