Stainless Steel and Rebar

A.Bill Palmer, president of Complete Construction Consultants in Lyons, Colo., responds: Stainless tie wire can cost six times as much as standard tie wire. Unless you’re trying to avoid potential rust spots (in places where the tie wire gets too close to the surface of the concrete) or have a few spare rolls, it’s not a very economical choice. You may be worried about galvanic action — always a concern with dissimilar metals — but that’s not likely to be a problem when you’re wiring regular carbon steel rebar together with stainless steel ties. Some types of stainless steel are actually pretty close to carbon steel on the galvanic scale, while other types of nonmagnetic stainless steel with higher levels of noble metals — like chromium and nickel — are further away and therefore more likely to react galvanically with it. Either way, the quantities of stainless steel are too small to lead to significant corrosion damage. And since tie wire’s only function is to position the rebar while concrete is being placed, corrosion wouldn’t affect the integrity of the structure anyway.

A related question is whether it’s acceptable to use regular carbon-steel tie wire with stainless steel rebar. SS rebar is often used in extremely corrosive environments like coastal areas, and while corroded tie wires wouldn’t matter structurally, they might pose a cosmetic problem and raise concerns about the quality of the concrete work. SS rebar is also often specified for hospital and research facilities because of its nonmagnetic properties; for these projects nonmagnetic stainless steel tie wire should be used.