Even After Three Days in Saltwater, No Damage: Magnesium Alloy Corrosion Reduced to One-Sixtieth [Reading Science]

UNIST Encapsulates Iron Impurities in Particles
Potential to Reduce Dependence on High-Purity Materials

A new technology has been developed that reduces the corrosion rate of magnesium alloys, which are lightweight but have been limited in use due to their tendency to corrode easily, to as low as one-sixtieth of the conventional level. Instead of removing the iron impurities that cause corrosion, the technology encapsulates them with another material, preventing them from coming into contact with magnesium—a reversal of conventional approaches.

On August 12, the Ulsan National Institute of Science and Technology (UNIST) announced that the research team led by Professor Sungsoo Park of the Department of Materials Science and Engineering has developed a highly corrosion-resistant magnesium alloy by trapping iron impurities within small particles inside the alloy.

Comparison of corrosion levels between the developed magnesium alloy and the conventional magnesium alloy after immersion in saltwater. Provided by the research team

Magnesium is the lightest among structural metals, making it highly promising for applications in fields where weight reduction is crucial, such as automobiles, aircraft, drones, and portable electronic devices. However, its major drawback is that it corrodes easily when exposed to water or salt.

In particular, the trace amounts of iron contained in magnesium raw materials are a primary cause of corrosion. When iron comes into direct contact with magnesium, the surrounding magnesium dissolves first, accelerating the damage to the surface. Traditionally, this has been addressed by using high-purity magnesium raw materials with the lowest possible iron content.

Corrosion Inhibition Mechanism Using Core-Shell Structure (Micro-Galvanic Corrosion). Provided by the Research Team

In contrast, the research team chose not to eliminate the iron, but to seal it off from direct contact with magnesium. By adding a small amount of scandium to the magnesium alloy, they utilized a principle where iron-rich particle cores are surrounded by a shell of scandium compound with little to no iron—a core-shell structure. The team conducted theoretical calculations with various elements and selected scandium as the optimal additive.

Experimental results showed that magnesium-aluminum alloys without scandium suffered severe corrosion after being immersed in saltwater for three days, whereas the alloy with scandium exhibited negligible structural changes.

Iron ‘sealed away’ rather than removed: Overcoming the limits of high-purity raw materials

The corrosion rate, as measured by weight change, decreased from 22.2 mm per year to 0.38 mm per year, a reduction to about one-sixtieth of the original rate. Even with a trace amount of scandium added to commercial magnesium alloys, the corrosion rate was reduced to one-seventh of the previous level.

Research team photo. Professor Sungsoo Park of UNIST (left) and researcher Jeongki Kim. Courtesy of UNIST

Notably, the new alloy exhibited a slower corrosion rate than ultra-high purity magnesium alloys, even though it contained more than six times as much iron impurity. The research team evaluated this as proposing a new alloy design that breaks away from the conventional approach of relying on expensive high-purity raw materials to enhance corrosion resistance.

Professor Park said, "Until now, there has been a strong perception that maximizing corrosion resistance in magnesium-based materials requires expensive high-purity raw materials with the lowest possible iron content. This technology can decrease dependence on costly ultra-high purity sources and enhance the industrial competitiveness of magnesium materials."

The research results were published online in the international journal Science Advances on July 23. The project was supported by the Ministry of Science and ICT and the National Research Foundation of Korea, among others.

This content was produced with the assistance of AI translation services.