I would think, the best way to stop rust, would be to start with a VERY good coat of primer. If you make sure the surface is prepped right, and then coat the whole thing with a good coat of primer, followed by several good coats of paint, it should last quite a while...
Finnegan - same techniques as used in auto body repair. Sand to bare metal and remove ALL rust and smooth out pits. Sand to at least 2" beyond the rusted area. Smooth the area with a finer grit sandpaper. Remove all dust. Spray with a good quality primer. Let dry. (I use a 2nd coat of primer - most don't). Make sure primer is dry. Then spray with a good guality paint. Use as many coats of paint as you care to, making sure each coat is dry before adding another. For a good, quality job I usually apply 3 coats of paint. Then lacquer if you want for sealing paint and add shine. Wax for protection and to keep off snow.
There is a product that turns rust into a hard black substance that is sandable and paintable. I've used for a few thing and it seems to convert the rust and stop it from coming back. The only problem is I can't remember what it was called. The first stuff I used was in a squeeze bottle. It was a mess and hard to apply. The last stuff I got was in a aerosol can. That is what I would recomend. It was easy to apply.
Hmmmmm, saw a 55 gal. drum in the chemical room at work the other day. It said "Acidene" on it. "Rust and scale remover". Now I'll have to read the label, and see just what kind of acid is in it. It might be muratic acid, but in my experience, muratic is used to etch concrete before applying paint or sealer.
One of the products that turns rust into a black sandable primer is called Extend. You can find it at Auto-zone, Pep Boys, Wall-mart .I've used it quite a bit over the last several years. It stops the rust from continuing the oxidation process (must be top coated, to last). I'd go with Mick's suggestion just use this before priming and prime with only one coat.
Turns out the packaging slip was still taped to the 55 gal drum of "Acidene". Along with the MSDS.
There are 2 ingredients listed. One is water, 82%...
The other 18% is HYDROCHLORIC ACID.
The instructions say to dip the parts in the solution, and promptly rinse with lots of water. It says it can be brushed on too, then rinsed. A respirator, rubber gloves, and a face shield are MUSTS. I should have know it was potent stuff on metal considering it's in a plastic 55 gal. drum.
~Chuck aka "toxic paint guy" and now "acid guy" too I'm sure.. ;-)