Instead of a rust preventer. (Like the 3m Rust Fighter which never really dries and looks like <img src="/forums/images/graemlins/butwiggle.gif" alt="" />.)
Look into the SIMS tintable spay-in bedliner.
I guarantee nothing will rust, you can'nt chip it off, plus you can pick the color.
It's a little more exspensive, however you can spray it from the same gun you would use for the rust preventer and have a job that lasts longer and looks a hole lot better. <img src="/forums/images/graemlins/kewl.gif" alt="" />