Originally Posted by TimJ

There's a couple products you can use to treat the rust first. Phosphoric acid is sold as a rust converter, you can check any product sold as a "rust away" sort of thing and if ti says phosphoric acid as the main ingredient then it's a converter. What it does is change the iron oxide to iron tannate, which apparently is stable so it basically kills the rusting process. Just scrub out all the rust you can and then try to get some acid on all the rusted spots, letting is stay in contact for a few minutes at least. The rust turns black and that's when it's been changed. Rinse it with water once you're done.

Then there's oxalic acid which basically just dissolves iron oxide. It's sold as wood bleach (powdered substance) and it works awesome for saoking rusted chrome parts in- they come out shiny and new looking. You could also soak a whole frame if you had a plastic garbage can to do it in. With that stuff use it as a concentration about 1/4 what is recommended for wood bleaching. It's a weak acid and I don't think it's necessary to rinse afterward, but it wouldn't hurt to do it.

After you've treated the rust and the frame is dry, then spray it with framesaver.

Or the more ghetto solution that might work well enough is just get some wd-40 and spray/scrub all the rust you can from the frame, then spray some more, basically rinsing the frame with wd-40, and once it's dry shoot some framesaver in there.