Corrosion Resistance of AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) High Entropy Alloys in NaCl and H2SO4 Solutions

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.

Al0.25CoCrFeNiV High Entropy Alloy Coating Deposited by Laser Cladding on Stainless Steel

“…In the as-cast sample in a dendritic (D) matrix (light gray phases in Figure 1 a,b), a V-rich phase is present in the form of coarse dendrites and precipitates along grain boundaries (dark gray phases in Figure 1 a,b). This is consistent with the data of [ 25 , 27 ], which indicate that V is prone to segregation into a separate phase.…”

“…The aim of this work is to develop a technique for applying HEACs using laser cladding. Al 0.25 CoCrFeNiV was chosen as the coating material because the addition of V increases the hardness and wear resistance of the base HEA AlCoCrFeNi [ 24 , 25 , 26 ] and positively affects the corrosion resistance in a sulfuric acid solution [ 27 ]. Considering that vanadium is prone to segregation into a separate phase, from our point of view, it is the use of laser cladding that should contribute to obtaining a defect-free coating with good adhesion to the matrix material.…”

Corrosion resistance of nonequiatomic FeNiCrMnAlx high entropy alloys in hexamine as inhibitor in 3.5% NaCl

“…It is necessary to obtain either single‐phase alloys or samples in which each phase contains a sufficiently high percentage of corrosion‐resistant elements. [ 52 ] The Al 15 HEA demonstrates the lowest corrosion resistance, which can be attributed to its phase structure. Specifically, the corrosion resistance of the FCC structure is generally higher than that of the FCC/BCC structure, particularly in terms of pitting corrosion resistance.…”

“…[51] Due to Cr's higher tendency to segregate, the higher segregation regions exhibit an increase in corrosion resistance, thereby increasing their ability to withstand aggressive environmental influences. [52] The corrosion resistance of the produced passive film is worsened when the Al content of the phase increases and the Cr concentration decreases. As a result, the Cl − ion will attack both the Alrich and Cr − depleted phases more frequently.…”

Corrosion Resistance of Al0.5CoCrFeNiCuxAgy (x = 0.25, 0.5; y = 0, 0.1) High-Entropy Alloys in 0.5M H2SO4 Solution

“…Liu et al [25] also observed the positive effect of Cu on the corrosion behavior of a number of Al x CoCrCuFeNi HEAs, not only in salt but also in alkaline solutions. On the contrary, Pratskova et al [26] noted that an excess concentration of copper adversely affects the corrosion resistance of Al 0.25 CoCrFeNiCu HEA in H 2 SO 4 solution, since copper-rich areas are most exposed to sulfuric acid. Thus, more research is still required to analyze the effect of copper on the corrosion resistance of Al x CoCrFeNi-based HEAs.…”