Highlights
- Landmark study by Zengin and Hassel explores complex interactions between rare earth elements and magnesium alloys’ corrosion properties.
- Different rare earth elements demonstrate varying effects on corrosion resistance, with scandium emerging as a particularly promising element.
- Commercial readiness remains challenging due to supply chain limitations, high costs, and processing complexities despite significant technical potential.
A landmark review by Hüseyin Zengin (opens in a new tab) and Achim Walter Hassel (opens in a new tab), based at Johannes Kepler University Linz and Faculty of Medicine and Dentistry, Department Physics and Chemistry of Materials, Danube Private University, surveying the complex and often contradictory role of rare earth elements (REEs) in modifying the corrosion properties of magnesium (Mg) alloys. Published in Corrosion Science (opens in a new tab) (Vol. 249, June 2025), this study offers the most comprehensive synthesis to date on how REEs interact with Mg to either exacerbate or mitigate corrosion—insights that could reshape alloy design across aerospace, automotive, and biomedical sectors.
Key Thesis
The central thesis is that the corrosion behavior of Mg-REE alloys is governed by each REE’s solid solubility in magnesium and the resultant intermetallic microstructures. REEs with low solubility, such as lanthanum (La) and cerium (Ce), tend to form cathodic intermetallic particles that increase micro-galvanic corrosion, particularly in Mg-Zn alloys. However, in Mg-Al alloys, these same REEs may improve corrosion resistance by refining microstructure and forming protective oxide layers.
Medium-solubility REEs like yttrium (Y), samarium (Sm), and ytterbium (Yb) show dual behaviors: they can enhance corrosion resistance when dissolved homogeneously, but their intermetallic forms can accelerate corrosion if distributed unevenly. High-solubility REEs—particularly scandium (Sc), gadolinium (Gd), and dysprosium (Dy)—are more promising, as they integrate smoothly into the Mg matrix, stabilize surface films like Sc₂O₃ and Gd₂O₃, and suppress corrosive reactions at the metal-electrolyte interface.
Findings
Scandium emerges as a standout, demonstrating exceptional corrosion inhibition, grain refinement, and even the ability to transform Mg into a body-centered cubic (BCC) structure, reducing its corrosion susceptibility. Sc also shows the lowest toxicity among REEs—making it a prime candidate for biomedical implants. Yttrium and neodymium, commonly used in commercial alloys like WE43, support durable oxide layer formation and provide stable, long-term corrosion resistance. Meanwhile, praseodymium and samarium show corrosion resistance benefits at trace levels but reverse course at higher concentrations due to harmful intermetallic formations. Erbium adds value, particularly in Zn- or Al-containing systems, promoting stable surface films and reducing micro-galvanic coupling.
The authors emphasize that corrosion resistance is not just about which REE is added but how it’s processed. Heat treatments and mechanical processing like extrusion can dissolve harmful intermetallics into the matrix and homogenize the microstructure, thereby neutralizing galvanic effects. Without such post-processing, even beneficial REEs can degrade performance. The composition and structure of surface films are equally critical. REE-derived oxides like Sc₂O₃, Y₂O₃, and Nd₂O₃ significantly enhance chemical stability and reduce chloride ion permeability, forming a durable corrosion barrier in aggressive environments.
Some Considerations
This review presents a critical inflection point for Mg alloy development. If alloy designers can exploit the electrochemical behaviors of specific REEs—especially Sc, Y, and Gd—they could usher in a new era of lightweight, corrosion-resistant materials for implants, aircraft, and energy storage applications. But barriers remain. Most findings are based on lab-based immersion and electrochemical tests under idealized conditions. Long-term environmental degradation and in vivo biocompatibility remain untested for many REEs. Furthermore, the prohibitive cost and limited availability of high-performing elements like Sc and Gd create supply chain and scalability challenges that are not yet resolved. Toxicological data for many REEs also remain insufficient, especially in biomedical contexts.
Commercial Readiness?
Commercial readiness is still on the horizon. Alloys like WE43 have found niche applications, but supply chain fragility, high costs, and processing complexity stall broader industrial adoption of REE-based Mg alloys. The next steps require deeper alloy optimization for large-scale production, life-cycle cost modeling, and integrated sourcing strategies. Regulatory hurdles—particularly for medical-grade applications—will also need to be addressed.
To conclude, REE-Mg alloys offer a technically compelling but commercially immature class of materials. With targeted R&D and supply chain engineering, they could bridge the gap between laboratory promise and real-world impact. Until then, they remain a high-value frontier—poised for breakthroughs in the right hands, but a way out.
Leave a Reply