Abstract
The electrochemical behavior of as-cast AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) high entropy alloys (HEAs) in 1 M NaCl and 0.5 M H2SO4 solutions is studied. Polarization measurements were carried out in a standard three-electrode electrochemical cell with a platinum auxiliary electrode using a P-30J potentiostat device. The potentials were measured relative to a saturated silver chloride reference electrode EVL-1M3 at room temperature (25 °C) with a sweep rate of 5 mV/s. It is shown that despite a wide passivation region, Al0.5CoCrFeNi1.6Ti0.7 HEA undergoes significant corrosion in both sodium chloride and sulfuric acid solutions and exhibits low corrosion potential and current density. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that Ti-containing eutectic areas are the most susceptible regions to corrosion. Intergranular corrosion was found in Al0.25CoCrFeNiMn and Al0.25CoCrFeNiCu HEAs. Moreover, Al0.25CoCrFeNiCu possesses the smallest passivation interval ΔE among all the investigated HEAs. For samples with Ti, Mn, and Cu, a protective film layer is not formed on the surface of the phases enriched in these elements, or it is brittle and crumbles. For samples with Si and V, a passivating film is formed. Thus, Al0.45CoCrFeNiSi0.45 and Al0.25CoCrFeNiV HEAs exhibited the highest resistance in 1 M NaCl and 0.5 M H2SO4 corrosive environments, respectively.
Highlights
For about 20 years, high entropy alloys (HEAs) have been highly studied by specialists in the field of materials science
The corrosion potentials obtained from the polarization curves are more negative values compared to the stationary potentials measured under no-current conditions, of the 13 powhich can be explained by the fact that the polarization curves were recorded 4in tentiodynamic mode with a certain potential sweep rate
All the investigated samples in this study showed inferior corrosion behavior than that of Alx CoCrFeNi HEA [20,21] and SS
Summary
For about 20 years, high entropy alloys (HEAs) have been highly studied by specialists in the field of materials science. This, in turn, caused a surge in studies of the behavior of HEAs at ultralow [8,9,10] and high temperatures [11,12,13,14], as well as their behavior in aqueous solutions of alkalis, acids, and salts [15,16,17,18,19]. The latter is substantiated by the possibility of applying corrosion-resistant coatings of HEAs on the surface of materials operating in aggressive aqueous solutions [20]. Based on the results of the analysis of the literature data, Shi et al [19] pointed to the HEA of the composition Co1.5 CrFeNi1.5 Ti0.5 Mo0.1 , which in a 1 M NaCl solution showed a corrosion current of the order of 0.13 × 10−6 A/cm , and the corrosion potential turned out to be
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