Tim - check out the electrolytic rust removal process. A penetrating oil like WD40 does nothing to the rust other than slow/prevent further oxygen being available to the process.

Electrolytic removal does free the iron in the rust molecule nearest the good metal, and in theory that one atom bonds back to the good metal. The destruction of that rust molecule then leaves all other rust molecules that were attached to the first one free to 'fall off'. Whats gone is gone though, and nothing can convert the rest of the rust back to iron and re-attach it in the exact spot it came from..

The process physically removes the rust from the metal with no mechanical interference, and no further loss of the base material. It's a simple process, there are no nasty chemicals or acids involved, and the results have to be seen. In my opinion it's well worth investing an hour of your time to experiment with if you ever have the need to remove serious rust from anything.

Especially seeing as it's virtually free..