Originally Posted by
JohnDThompson
At Trek we used a hot phosphoric acid bath on bare frames. Phosphoric acid was particularly suited for that purpose as it dissolves rust much more rapidly than it does the base metal and it simultaneously etched the surface to provide an ideal bonding surface for paint. A hot phosphoric acid bath might not be practical in your home, but consumer products such as "Naval Jelly" also contain phosphoric acid as the active ingredient and may suit your needs.
Naval Jelly is the way to go. It preferentially dissolves rust faster than the bare metal underneath. The other acids will eat up the good metal just as quickly once it gets past the rust, not a good thing.
Originally Posted by
mixtemaniac
oxalic acid. search the classic & vintage forums for more info.
Sure, you can also use an 80-grit pad on a high-RPM grinder to remove paint from the frame as well. But the results won't be as nice or optimal as using a chemical paint-stripper. Who cares about a couple of holes in the tubing, the paint & rust is gone right?