Q: Can stainless steel tie wire be used with standard rebar?

A: Galvanic action is always a concern when using dissimilar metals, but it's not likely to be a problem when using stainless tie wires with regular carbon steel rebar.

First, to determine whether galvanic action is likely, you would need to know the type of stainless steel. There are many different kinds; some are pretty close to carbon steel on the galvanic scale while others are not. One way to tell is if the stainless is not magnetic. Nonmagnetic stainless steel has higher levels of chromium, nickel, and other more noble metals, and could have a galvanic reaction in some situations.

But more importantly, the quantity of stainless steel in tie wire is so small that even if galvanic action corroded the carbon steel, it is unlikely that enough corrosion byproducts would be produced to damage the concrete. Because tie wire's only function is to position the rebar while concrete is placed, corrosion wouldn't affect the integrity of the structure.

However, stainless tie wire can cost as much as six times more than standard tie wire. So unless you're trying to avoid potential rust spots if the tie wire gets too close to the surface of the concrete, it's unlikely you'd want to use it.

A related question is whether it's acceptable to use regular carbon steel tie wire with stainless steel (SS) rebar. SS rebar often is used in extremely corrosive environments, such as coastal construction, and in MRI and research facilities because of its nonmagnetic properties. It wouldn't matter structurally if the tie wires corroded, but it might be a cosmetic problem and raise concerns about the quality of the concrete work.

More importantly, though, stainless steel tie wire should always be used when the structure's magnetic signature is an issue. Stainless steel tie wire should be used with stainless steel reinforcing, especially to bundle stainless bars for shipment. Otherwise, the galvanic action of carbon steel tie wire will corrode and the bundles will come apart.

Thanks to Kevin Cornell, Salt Specialty Rebar, and Fred Goodwin, BASF, for contributing to this answer.