Startup enables 100-year bridges with corrosion-resistant steel

According to the American Road and Transportation Builders Association, one in three bridges needs repair or replacement, amounting to more than 200,000 bridges across the country. A key culprit of America’s aging infrastructure is rebar that has accumulated rust, which cracks, and then breaks apart, the concrete around it, making bridges more likely to collapse.

Now Allium Engineering, founded by two MIT PhDs, is tripling the lifetime of bridges and other structures with a new technology that uses a stainless steel cladding to make rebar resilient to corrosion. By eliminating corrosion, infrastructure lasts much longer, fewer repairs are required, and carbon emissions are reduced. The company’s technology is easily integrated      into existing steelmaking processes to make America’s infrastructure more resilient, affordable, and sustainable over the next century.

“Across the U.S., the typical bridge deck lasts about 30 years on average — we’re enabling 100-year lifetimes,” says Allium co-founder and CEO Steven Jepeal PhD ’21. “There’s a huge backlog of infrastructure that needs to be replaced, and that has frankly aged faster than it was expected to, largely because the materials we were using at the time weren’t cut out for the job. We’re trying to ride the momentum of rebuilding America’s infrastructure, but rebuild in a way that makes it last.”

To accomplish that, Allium adds a thin protective layer of stainless steel on top of traditional steel rebar to make it more resistant to corrosion. About 100,000 pounds of Allium’s stainless steel-clad rebar have already been used in construction projects around the U.S., and the company believes its process can be quickly scaled alongside steel mills.

“We integrate our system into mills so they don’t have to do anything differently,” says Jepeal, who co-founded Allium with Sam McAlpine PhD ’22. “We add everything we need to make a normal product into a stainless-clad product so that any mill out there can make a material that won’t corrode. That’s what needs to happen for all of the world’s infrastructure to be longer lasting.”

Toward better bridges

Jepeal completed his PhD in the MIT Department of Nuclear Science and Engineering (NSE) under Professor Zach Hartwig. During that time, he saw Hartwig and fellow NSE researchers spinout Commonwealth Fusion Systems to create the first commercial fusion reactors, which he says sparked his interest in startups.

“It definitely helped me catch the startup bug,” Jepeal says. “MIT is also where I got my materials science chops.”

McAlpine completed his PhD under Associate Professor Michael Short. In 2019, McAlpine and Short were working on an ARPA-E-funded project in which they would combine metals to improve corrosion-resistance in extreme environments.

Jepeal and McAlpine decided to start a company around applying a similar approach to improve the resilience of metals in everyday settings, working with MIT’s Venture Mentoring Service and speaking with Tata Steel, one of the largest steel makers in the world that has worked with the MIT Industrial Liaison Program (ILP). Members of Tata told the founders that one of their biggest problems was steel corrosion.

A key early problem the founders set out to solve was depositing corrosion-resistant material without adding significant costs or disrupting existing processes. Steelmaking traditionally begins by putting huge pieces of precursor steel through machines called rollers at extremely high temperatures to stretch out the material. Jepeal compares the process to making pasta on an industrial scale.

The founders decided to add their cladding before the rolling process. Although Allium’s system is customized, today the company makes use of existing pieces of equipment used in other metal processing applications, like welding, to add its cladding.

“We go into the mills and take big chunks of steel that are going through the steelmaking process but aren’t the end-product, and we deposit stainless steel on the outside of their cheap carbon steel, which is typically just recycled scrap from products like cars and fridges,” Jepeal says. “The treated steel then goes through the mill’s typical process for making end products like rebar.”

Each 40-foot piece of thick precursor steel turns into about a mile of rebar following the rolling process. Rebar treated by Allium is still more than 95 percent regular rebar and doesn’t need any special post-processing or handling.

“What comes out of the mill looks like regular rebar,” Jepeal says. “It is just as strong and can be bent, cut, and installed in all the same ways. But instead of being put into a bridge and lasting an average of 30 years, it will last 100 years or more.”

Infrastructure to last

Last year, Allium’s factory in Billerica, Massachusetts, began producing its first commercial cladding material, helping to manufacture about 100 tons of the company’s stainless steel-clad rebar in collaboration with a partner steel mill. That rebar has since been placed into construction projects in California and Florida.

Allium’s first facility has the capacity to produce about 1,000 tons of its long-lasting rebar each year, but the company is hoping to build more facilities closer to the steel mills it partners with, eventually integrating them into mill operations.

“Our mission of reducing emissions and improving this infrastructure is what’s driving us to scale very quickly to meet the needs of the industry,” Jepeal says. “Everyone we talk to wants this to be bigger than it is today.”

Allium is also experimenting with other cladding materials and composites. Down the line, Jepeal sees Allium’s tech being used for things beyond rebar like train tracks, steel beams, and pipes. But he stresses the company’s focus on rebar will keep it busy for the foreseeable future.

“Almost all of our infrastructure has this corrosion problem, so it’s the biggest problem we could imagine solving with our set of skills,” Jepeal says. “Tunnels, bridges, roads, industrial buildings, power plants, chemical factories — all of them have this problem.”