Yes, they use this in large steel ocean vessels. Also, you can purchase zinc strips that are intended to prevent steel roofs from rusting. Yes it works but it works on the process of electrolysis which means you need an electrical connection between the zinc and the steel that will be protected.
Being a gearhead living on a low budget in the ever worsening rust belt has given me a unique hatred for rust.
Something I've found to work very effectively is Zinc Rich or Cold Galvanizing primer. I use it now on all my fabrications and it helps A LOT. You can buy it from rustoleum in two grades, expensive one is compatible to all types of paint, cheap one requires a latex topcoat because it is incredibly porous. I've seen on one or two occasions that it's available by the quart or gallon from hardware stores for use on barn roofs. I've never used this brush on stuff.
I've been using the more expensive grade of rattle can rustoleum for about 4 years and I've been very pleased. Note, once again, best practice is for the zinc to be directly against the metal.
