Abstract

Magnesium (Mg) alloys offer high weight-saving potential for transportation technologies; However, their use remains constrained by poor corrosion resistance, which is strongly dependent on alloy purity. The presence of impurities, such as iron (Fe), severely degrades the corrosion resistance of Mg alloys. Herein, we present an alloy design strategy that substantially improves the corrosion resistance, even when using low-purity Mg. Our method produces core-shell particles, where an Fe-rich core is encapsulated by an Fe-depleted shell embedded in the Mg matrix. This shell acts as a local microscavenger that isolates the core and suppresses impurity-triggered corrosion, resulting in corrosion resistance achievable only when using ultrahigh-purity Mg. This approach provides a practical pathway for the development of high-performance Mg alloys without relying on costly purification.

Magnesium (Mg) is prized for its exceptionally low weight, but its tendency to corrode has limited its wider use in cars, aircraft, drones, and other applications where lighter materials could offer significant advantages. Even trace amounts of iron (Fe) can accelerate that corrosion, making material purity a critical—and costly—part of producing durable Mg alloys.

Professor Sung Soo Park and his research team in the Department of Materials Science and Engineering at UNIST approached the problem differently. Rather than removing Fe impurities, they designed the alloy to isolate them and limit their ability to trigger corrosion. The resulting material encloses Fe-rich regions within specially formed particles and maintains strong corrosion resistance despite being made from lower-purity Mg.

The researchers achieved this by adding a small amount of scandium (Sc) to a magnesium-aluminum (Mg-AI) alloy. As the alloy solidifies, Fe becomes concentrated at the center of microscopic particles, surrounded by an outer layer containing very little Fe. This core–shell structure separates the Fe-rich center from the surrounding Mg, preventing it from readily initiating corrosion.

The team identified scandium through theoretical calculations that screened a range of elements for their ability to produce the desired structure. Rather than reducing the total amount of iron, the strategy controls how the impurity is distributed within the alloy.

The difference was clear in saltwater tests. After three days of immersion, the Mg-AI alloy without scandium showed severe corrosion, while the scandium-containing alloy largely retained its original form. Its corrosion rate fell from 22.2 millimeters per year to 0.38 millimeters per year, nearly a 60-fold reduction.

The approach also proved effective in a commercial Mg alloy. Adding only a trace amount of scandium reduced its corrosion rate to about one-seventh that of the original alloy, suggesting that the strategy could extend beyond the experimental material.

Notably, the newly designed alloy contained more than six times as much Fe as an ultrahigh-purity Mg alloy, yet corroded more slowly. The result shows that corrosion resistance depends not only on how much Fe is present, but also on how that Fe is distributed within the material.

“Mg alloys have traditionally required expensive, high-purity raw materials with extremely low Fe content to achieve strong corrosion resistance,” said Professor Park. “Our findings show that controlling how Fe is distributed within the alloy offers another way to address the problem.” He further added, “Reducing the need for ultrahigh-purity magnesium could lower material costs and help expand the practical use of lightweight magnesium alloys.”

The findings were published online in Science Advances on July 23. The research was supported by the Ministry of Science and ICT (MSIT) and the National Research Foundation of Korea (NRF), among other funding sources.

Journal Reference

Jeong-Ki Kim, Jaeho Kwon, Du-Won Min,  et al ., “Core-shell particle engineering overturns conventional purity-corrosion dependence in Mg alloys,”  Sci. Adv.,  (2026).