Key Takeaways & Executive Findings
- •• Ce micro-alloying significantly enhances the corrosion resistance of as-cast CoCrNi MEAs in 3.5wt.% NaCl solution, with optimal performance at 0.02at.% Ce. • The addition of Ce reduces the passivation current density to a minimum of 26.383 μA·cm-2 and increases the breakdown potential to 0.471 VSCE, indicating superior protective film stability. • The improvement is attributed to Ce modifying inclusions and forming a non-conductive precipitated phase, which enhances the passivation film's protective properties. • This cost-effective micro-alloying strategy offers a promising route for improving the durability of CoCrNi MEAs in corrosive environments, with potential applications in aerospace, automotive, and marine industries.
Abstract
Enhancing corrosion resistance in cast alloys using straightforward and cost-effective micro-alloying techniques has emerged as a key area of investigation in materials science. The challenge lies in applying this technique to further enhance the already excellent properties of CoCrNi medium-entropy alloys (MEAs) for casting applications. A micro-alloying approach was proposed to improve the corrosion resistance of as-cast CoCrNi MEAs by incorporating cerium (Ce). The corrosion resistance of CoCrNi MEAs firstly increases and then decreases as the Ce content increases in a 3.5wt.% NaCl solution. At a Ce content of 0.02at.%, the passivation current density reaches its minimum value (26.383 μA·cm-2), while the breakdown potential reaches its maximum (0.471 VSCE), imparting exceptional corrosion resistance. The results indicate that the enhanced corrosion resistance is primary due to Ce micro-alloying, which affects inclusions by forming a non-conductive precipitated phase and modifying the passivation film. Ce micro-alloying presents a promising strategy for enhancing the corrosion resistance of as-cast CoCrNi MEAs.
1. Introduction
Medium entropy alloys (MEAs), especially those based on CoCrNi, have gained significant attention in materials science due to their unique combination of properties [1-6]. CoCrNi MEAs, characterized by a nearly equiatomic composition of cobalt (Co), chromium (Cr), and nickel (Ni), offer an advantageous balance of mechanical strength, ductility, and resistance to high-temperature oxidation and corrosion, setting them apart from conventional alloys [7-13]. Moreover, corrosion resistance plays a critical role in determining the durability and reliability of cast alloys in various industrial settings, including aerospace, automotive, and marine environments [14]. Enhanced corrosion resistance can extend service life, reduce maintenance costs, and elevate safety standards, making it a focal point of ongoing research. Consequently, the development of innovative alloying strategies remains essential to further improve the corrosion resistance of these advanced materials.
Micro-alloying, which involves the addition of trace amounts of specific elements (<0.1%), introduces an innovative strategy for enhancing the properties of alloys. This technique can profoundly affect the microstructure and phase constitution of the base alloy, ultimately leading to superior performance attributes. Whether incorporating rare-earth elements (REs) or common metallic elements, such as aluminum (Al), iron (Fe), Cr, or Ni, the objective is to optimally dope MEAs and high-entropy alloys (HEAs) [15-19]. Presently, additional research is imperative to comprehensively understand the utilization of REs, specifically cerium (Ce)-doped MEAs/HEAs. Improving the corrosion resistance of MEAs/HEAs is a paramount objective, and the potential for enhancing other properties through the incorporation of REs merits further exploration. Furthermore, if the addition of REs proves equally effective in bolstering other properties, their cost implications must also be taken into account. The incorporation of REs is recognized for refining grain structures, augmenting mechanical properties, and substantially enhancing corrosion resistance. Notably, Ce has demonstrated remarkable effects on the corrosion resistance of metallic alloys [20-23]. It is well-documented that Ce promotes the formation of fine, equiaxed grains during solidification, which can enhance the mechanical properties and uniformity of the alloy. Moreover, Ce can form stable oxides that serve as protective barriers on the alloy surface, thereby augmenting its resistance to corrosion. For instance, Ce has been successfully employed to enhance the corrosion resistance of aluminum, magnesium, and steel alloys by forming a stable and adherent oxide layer that safeguards the underlying metal from corrosive environments [24, 25]. Research on the specific impacts of Ce on CoCrNi MEAs is still in its nascent stages. Preliminary studies have indicated substantial potential for enhancing mechanical strength, ductility, and resistance to high-temperature oxidation. The present research endeavors to fill this gap by systematically investigating the effect of Ce micro-alloying on the corrosion behavior of as-cast CoCrNi MEAs in a 3.5wt.% NaCl solution.
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Bo Chen, Chang Ma, Wei-dong Xuan, Zhan-yong Gao, Guang-rui Zhang, Fei Lu, Yuan Hou (2026). Micro-alloying for improving corrosion resistance of as-cast alloy CoCrNi in 3.5wt.% NaCl solution by Ce addition. SinoTechIntel Verified Research. https://doi.org/10.1007/s41230-026-4218-2
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Frequently Asked Questions
What is the optimal cerium content for enhancing corrosion resistance in CoCrNi medium-entropy alloys?
The optimal cerium content is 0.02 at.%, which results in the lowest passivation current density (26.383 μA·cm-2) and the highest breakdown potential (0.471 VSCE) in a 3.5wt.% NaCl solution.
How does cerium micro-alloying improve the corrosion resistance of CoCrNi alloys?
Cerium micro-alloying improves corrosion resistance by modifying inclusions and forming a non-conductive precipitated phase, which enhances the stability and protective nature of the passivation film on the alloy surface.
What are the potential applications of CoCrNi alloys with enhanced corrosion resistance?
These alloys can be used in aerospace, automotive, and marine environments where durability and reliability are critical, offering extended service life and reduced maintenance costs.
Is the micro-alloying technique cost-effective?
Yes, micro-alloying with trace amounts of cerium is a straightforward and cost-effective technique, making it a promising strategy for industrial applications.
What is the effect of cerium content on corrosion resistance?
The corrosion resistance of CoCrNi MEAs first increases and then decreases with increasing cerium content, with the best performance at 0.02 at.% Ce.
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