One startup’s paper-thin stainless steel could change how bridges are built

A new challenge in modern construction arises from an unexpected culprit: rust. Steel rebar, commonly used to reinforce concrete structures, faces corrosion that can lead to premature failure. This issue is particularly critical for bridges, which are constantly exposed to water and salt. Currently, about one-third of bridges in the United States require significant repairs or replacements, with projected costs nearing $400 billion in the next decade. Engineers have devised various methods to combat rust, such as applying epoxy coatings to rebar or increasing concrete coverage to delay water exposure. However, these strategies often fall short over time. The most effective way to mitigate rust is through the use of stainless steel rebar, but its high cost limits widespread adoption. Steven Jepeal, co-founder and CEO of Allium Engineering, explains that stainless steel is typically reserved for the most critical bridge designs due to its expense. Allium proposes a solution that strikes a balance: coating regular rebar with a thin layer of stainless steel. This innovation aims to extend a bridge's lifespan from 30 years to as much as 100 years. Co-founder and CTO Samuel McAlpine states, "As long as we’re getting full coverage of the surface, a thin layer is enough stainless steel to where it’s going to resist corrosion for hundreds or thousands of years." The startup’s stainless steel-enhanced rebar has already been utilized in several bridge repairs, including projects on Interstate 91 in Massachusetts and U.S. Highway 101 in California. Additionally, it has been implemented in a commercial boat yard in Key West, Florida. While engineers often specify stainless steel for high-traffic bridges—despite its cost being five times that of standard rebar—most projects typically rely on epoxy-coated rebar, which is only 25% to 50% more expensive than uncoated options. However, epoxy-coated rebar requires careful handling and maintenance, leading to additional costs. Allium is positioning its stainless-clad rebar as a viable alternative to epoxy-coated products, with aspirations to match or even undercut their pricing. Jepeal noted that the installation process could be more economical, as the rebar does not demand the same level of care and reduces the need for extra concrete typically used to protect against rust. This innovative approach could reduce cement usage by up to 10%, allowing transportation departments to consider greener cement alternatives that are less alkaline than traditional mixes. Allium’s manufacturing process involves cladding 7,000-pound steel billets with stainless steel, creating a robust outer layer through a controlled rolling process. Ultimately, Allium's method results in rebar that is not only cost-effective but also significantly more resilient against corrosion, promising a sustainable solution for future bridge construction and repair.