Researchers on NETL’s Structural Materials Team produced a more robust pipeline material for transporting H₂ and captured carbon dioxide (CO₂) by adding the rare earth element (REE) cerium to create a tougher steel alloy.

The accomplishment simultaneously addresses two important U.S. Department of Energy priorities: development of infrastructure needed for decarbonization and improvement of the critical minerals supply chain.

Researchers explained that the added cerium reacts with oxygen and sulfur impurities that are introduced during the steel manufacturing and eliminates the negative impact of those impurities, producing a steel that is less susceptible to cracking during its service life. Testing at NETL has shown that cerium additions to X90 pipeline steel can improve the Charpy impact toughness—a measure of the steel’s ability to absorb energy and resist crack propagation—by up to 50%.

“Such an improvement is important for new pipelines, where running ductile fracture is a major concern, such as for CO₂ transport. These results show promise, and more research is needed to determine the impact of cerium on other important steel properties such as weldability,” said NETL Research Scientist Richard Oleksak.

“Better steel isn’t the only potential benefit,” Oleksak said “Cerium, which is the most abundant rare earth element in both conventional and unconventional domestic feedstocks, is currently a major unused byproduct of the extraction of more valuable rare earths. This means we could see the creation of applications for cerium to meet industrial demand.”

He said that with global steel production at two billion tons annually, the incorporation of even small amounts of cerium into this industry would significantly increase its demand. By developing high-volume applications for cerium, the value proposition for domestic production of rare earths is improved, thereby enhancing the supply chain for these critical minerals.

REEs have a long history in iron and steelmaking. Specifically, cerium, lanthanum and cerium/lanthanum-rich alloys have been used in some form since the 1950s. The cost of cerium and lanthanum has decreased significantly since the major work involving these elements in iron and steelmaking in the mid-1900s.

A major driver of this cost reduction is related to the so-called rare earth balance problem. That is, both cerium and lanthanum co-occur with other REEs, such as neodymium, in both conventional and unconventional domestic feedstocks. Because of the high demand of neodymium and other REEs for various clean energy technologies, and the likely increase in demand for these technologies in the era of global decarbonization, it is very likely that tremendous amounts of unused cerium and lanthanum will be produced in the coming decades.

“This presents an excellent opportunity for the renewed consideration of these rare earths as promising and inexpensive alloy additions in steelmaking,” Oleksak said. “The success of NETL in developing cerium-enhanced steel alloys is an example of the potential economic and environmental benefits to come from acting on such opportunities.”

Significant new pipeline infrastructure improvements are expected within the coming years that can help the nation facilitate decarbonization goals, including pipelines specifically designed for CO₂ and H₂ transport. Both uses pose unique challenges and place increased reliance on the integrity of the steel products.