ArtMetal

I use roofing tar to coat the part of the metal which will be inside the concrete. Apply liberally and wrap it with plastic until installation. The reason for the plastic is because the roofing tar does not dry very well, and since you will be applying a thick coat, it likely not to dry until months later.

My understanding from talking with an architect is that the tar prevents the acidity from the concrete from passivation to the steel.