Rusted to strip down and repaint? I've got a 1984 Gitane Professional, Reynolds 531C , frameset that have been using on my trainer for the winter months. This bike hasn't been outside for at least 14 years and has developed some rusting at the junction of the seat, down, chainstay tubes, and bottom bracket. I'd like to restore this bike and was wondering what a good criteria would be for using, or disposing (keeping it on the trainer?), the frameset again? The fork is chromed as well as the chainstays.

get one of those rust removal wheels from an auto parts store, or your local wally-world. it attaches to a cordless drill. start going at the rust. if it's severely pitted, or totally rusted through, i'd say it's trash, especially since it's at such a critical point on the bike. if it's just a bit of surface rust, you can probably level it with some good primer, and repaint the frame.

You might want to try this.

If the rust is confined to the surface of the bike (and if it's confined to the bike's exterior), then it's easy enough to sand it off, touch it up with rust converter (which chemically converts rust to some other chemical compound that doesn't propagate) - this is a lot easier than setting up a charged solution as Joshua mentioned, although it will do a similar thing.

But if there is a lot of rust around the frame and it would be a PITA to remove it all, find a place that does sandblasting and painting. That's what I did on my Centurion Comp TA.
There was a lot of surface rust on the frame, all over, and I brought it to a place that does sandblasting and powdercoating. The blasting, if done right, removes all surface rust efficiently, and the metal is then clean for a repaint.

Here are pictures of the condition of my frame's paint job prior to sandblasting.

follow the instructions from Joshua. It is simple chemistry and it is probably better than sanding the metal away. if you read up for a little you'll understand how rust forms and how you can prevent it.