Key Takeaways & Executive Findings
- •• Sc addition induces formation of a (Ni, Co)2Sc Laves phase with FCC structure, which is preferentially corroded due to high electrochemical activity. • Sc significantly accelerates corrosion rate in 0.5 mol/L H2SO4, leading to poorer corrosion resistance compared to NaCl solution, with severe intergranular corrosion. • Passive films on Sc-containing alloys incorporate Sc2O3 and exhibit p-n junction electronic characteristics, with defect density increasing from 10^21 to 10^23 cm^-3 as Sc content rises. • The study provides critical insights for designing corrosion-resistant high-entropy alloys for acidic environments, guiding engineering applications.
Abstract
This study investigates the effects of varying Sc content on phase composition, corrosion resistance and passive film characteristic of Al1.2CoCrFeNiScx (x=0, 0.1, 0.2, 0.3) high-entropy alloys in 0.5 mol/L H2SO4 solution. The addition of Sc causes the alloys to form a Laves phase which is a (Ni, Co)2Sc intermetallic compound with face centred cubic (FCC) structure and lattice parameter of 0.695 nm. During the potentiodynamic polarization process, Laves phase is severely corroded due to its large grain orientation spread value and high electrochemical activity. Sc deteriorates the corrosion resistance of the alloy primarily by significantly accelerating the corrosion rate rather than altering the corrosion tendency. Al1.2CoCrFeNiScx alloys exhibit poorer corrosion resistance in 0.5 mol/L H2SO4 than in 3.5 wt.% NaCl solution, with severe intergranular corrosion observed on the alloy surface. The passive films on Sc-free alloys primarily composed of Al2O3 and Cr2O3, while for Sc-containing alloys, the film mainly contains Al2O3, Cr2O3 and Sc2O3. In addition, the passive films on Sc-free alloys behave as an n-type semiconductor, while the passive films on Sc-containing alloys surface exhibit the electronic characteristics of p-n junctions. As the Sc content rises, the defect density in passive film increases from 1021 cm−3 to 1023 cm−3, which leads to a less compact and less protective passive film, ultimately decreasing the alloy’s corrosion resistance. This work holds significant guiding significance for the engineering application of high-entropy alloys in acidic environments and is conducive to the development of high-performance corrosion-resistant alloys.
1. Introduction
High-entropy alloys (HEAs) have emerged as a significant innovation in materials science since their introduction by CANTOR et al [1] and YEH et al [2]. These alloys, composed of multiple principal elements, have led to the development of various types, including lightweight HEAs, 3d transition metal-based HEAs, and refractory HEAs [3, 4]. Among them, AlCoCrFeNi-based HEAs are notable as representative lightweight alloys, offering distinct advantages such as high strength, hardness, wear resistance, corrosion resistance, and excellent performance at elevated temperatures [5−7]. These properties make them highly attractive for high-performance applications, particularly in demanding environments such as the marine and chemical industries. While many of the researches on AlCoCrFeNi-based HEAs have focused on enhancing their mechanical properties, their corrosion behavior and mechanisms, especially in harsh acidic or saline environments, are equally critical.
The chemical composition of HEAs plays a crucial role in their corrosion behavior and resistance. KAO et al [8] obseved that Al reduces the corrosion resistance of AlxCoCrFeNi HEAs in 0.5 mol/L H2SO4 at temperatures above 27 ℃ due to the porosity and poor quality of the protection oxide film formed by Al in these alloys. While oxide film formation can protect the alloy, pitting corrosion occurs rapidly if the passive film is locally damaged. In chloride environments, LEE et al [9] found that Al negatively impacts pitting resistance, as it has lower pitting potentials. When Cl− ion was introduced to H2SO4 solution, pitting corrosion becomes more severe as Al content increases in Alx(CoCrFeNi)100−x alloys [8]. Cr is widely recognized as a beneficial element for corrosion resistance, owing to its ability to form a protective Cr2O3 passive film in 0.1 mol/L H2SO4 [10]. WU et al [11] investigated the influence of Ti content on the corrosion behavior of AlCoCrFeNi alloy in 3.5 wt% NaCl and HCl (pH=3) solutions, fi
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SUN Yuan-wei, YIN Zi-kang, WANG Zi-yi, ZHU Kun-jun, WANG Cheng-xu, ZHANG Quan, ZHAO Yan-yun, SUN Qi-jing (2025). Corrosion resistance and passive film characteristics of Sc-added Al1.2CoCrFeNi high-entropy alloys in sulfuric acid solution. Journal of Central South University. https://doi.org/10.1007/s11771-025-6112-2
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Frequently Asked Questions
What is the effect of Sc addition on the corrosion resistance of Al1.2CoCrFeNi high-entropy alloys?
Sc addition significantly accelerates the corrosion rate in 0.5 mol/L H2SO4 solution, leading to poorer corrosion resistance compared to Sc-free alloys. This is primarily due to the formation of a Laves phase (Ni, Co)2Sc, which is preferentially corroded, and an increase in defect density in the passive film.
What are the main components of the passive film formed on Sc-containing Al1.2CoCrFeNi alloys?
The passive films on Sc-containing alloys are mainly composed of Al2O3, Cr2O3, and Sc2O3, whereas Sc-free alloys have films primarily composed of Al2O3 and Cr2O3.
How does Sc content affect the electronic properties of the passive film?
Sc-free alloys exhibit n-type semiconductor behavior, while Sc-containing alloys show p-n junction characteristics. As Sc content increases, the defect density in the passive film increases from 10^21 to 10^23 cm^-3, making the film less compact and protective.
What is the significance of this study for engineering applications?
This study provides crucial insights into the corrosion behavior of high-entropy alloys in acidic environments, guiding the design of high-performance corrosion-resistant alloys for applications in marine and chemical industries.
What is the DOI of the paper?
The DOI is 10.1007/s11771-025-6112-2.
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