Hello all,

Working on one of the winter projects: Repainting the Trek 500 and after stripping the paint (99.7%) I found a lot of surface rust, the bubbly, pop the paint up kind. There is quite a bit around the lugs and along the top tube around the cable braze-ons.
I've been hitting it with a wire brush attachment for my drill and most of it's coming off, but now I've been through two batteries and my arms are tired. So I ask you this question:
Is there an acceptable amount of rust that can be left on when re-painting?
I've got an idea of what the answer will be, but before I head down to the hardware store for some oxalic acid I wanted to get some sort of definitive answer. Thanks.

Rob

You have to get rid of all the rust or you just have the same problem over and over again till the frame's too rotted to use.

Get rid of all the rust now and it wont be a problem later.

There is no acceptable amount of rust, and to quote an old rocker, 'Rust never sleeps'.

That's what I thought, thanks.

You could also try what's known as "electrolysis". It's a fairly easy process, and can be done relatively simply if you have the space, a battery charger, and a plastic "kiddie pool".

Here's a link to the basics:

https://www.stovebolt.com/techtips/ru..._derusting.htm

Thanks satbuilder. I will see if I can rustle up a battery charger and give it a go.

This is probably not a "purist" response, but there are also several "rust-kill" primers that supposedly turn remnants of rust inert and seal them so they're "deactivated." I know a couple of highly-regarded auto restorers who swear by these products, and I've used them on a couple of old bike frames myself. There are times when you just can't get to the stuff in the nooks and crannies, and you have to reconcile yourself to a reasonable compromise.

I have a can of that stuff, Permatex Rust Restorer, spray it on and it kills the rust and turns it black, but I still like to get rid of as much of the rust as possible first to make sure the metal is still sound.

And if I can get rid of it all without needing the rust restorer, so much the better.

If you are going for a full repaint, the best bet would be to find someone that can sand (media) blast it for you. To repeat what others said, any amount of untreated rust WILL come back to haunt you.
Depending on your budget , I recently had a frame blasted, dipped and powder coated in a solid (stock) color for $140. The last time I rattle can painted a frame I invested about $60-$75 alone in materials, paint, solvents, sanding papers, ect.