Concrete structures often rely on steel rebar for strength, but rust is their silent enemy. As water and salts seep into cracks, they corrode embedded rebar, which expands and cracks the concrete further. In U.S. bridges, roughly one-third are in need of replacement or major repair, largely due to corrosion. To counter this, more expensive stainless steel rebar is sometimes used but only in critical stretches, because of its high cost (around five times that of regular rebar).
Enter Allium Engineering, a startup that proposes a midway solution: regular steel rebar clad with a thin stainless steel shell, says TechCrunch. The idea is that a full stainless skin, if uniformly applied, can protect the steel beneath from corrosion for decades or even centuries. Their approach involves welding wires of stainless steel to a solid steel billet, then rolling it down to size so that the final product has just about 0.2 mm of stainless cladding.
They’ve already tested this in the field: on a bridge deck replacement along U.S. Highway 101 in California, and in a future project on Interstate 91 in Massachusetts. Because the cladding process is integrated with standard steel‐mill workflows, Allium believes it can keep its pricing competitive, especially compared with epoxy coatings that require special handling, patching, and extra concrete layers to shield rebar.
Using clad rebar reduces the need for excess concrete or protective barriers, which can cut cement use by up to 20%. The concept also opens the door for greener concrete mixes, as designers might be more open to low-alkalinity formulas when corrosion resistance is built into the steel layer.
Allium’s thin stainless steel shell could bridge the gap between durability and affordability, offering a more resilient option for infrastructure that faces salt, humidity, and aging over decades.