My 83 Schwinn is showing rust on the brake cable guides on the top tube, quite a bit of rust on the one farthest forward. I'm getting ready to replace the brake cables and want to treat the areas to prevent further damage. What do people use to remove spot rust and prevent it coming back? The bike has its original black paint. It's not a restoration project but it is my ride and I want to keep it in as good a shape as I can.

I used to use a product on various things and I'll provide a link. it used to be called something else. basically it bonds with the rust and converts it chemically so that the rusting stops. when it dries it turns black. then you can paint it. 1st you have to clean the rust the best you can. the product comes in sprays and jars/bottles so you can use a small model brush to apply discreetly. not sure if it would be good for your purpose but if you can clean the rust and smooth the guide surface then maybe to can apply a tiny bit of this stuff and after it dries apply cable lube.

Rust-Oleum Rust Reformer
https://www.amazon.com/s/ref=nb_sb_no...+Rust+Reformer

You might try some oxalic acid on them. Bar Keeper's friend can be mixed into a paste and put on the affected areas, this will neutralize the rust. Probably scrub some with a toothbrush or the like to help it along. Apparently Bar Keeper's friend also comes in a liquid, but I've never tried that. Wrap with some damp paper towels and let sit for awhile. When the rust is removed, I would clean and touch up the areas with something like Testor's enamel model paint to protect it. Let dry thoroughly, heat will help.

I sanded mine down and then repainted with touch up paint. Took some sand paper and wrapped it around a heavy gauge metal wire. Also covered up the surrounding area so I wouldn't damage the paint on the top tube.






You can also use Naval Jelly. It's like a thick gel. It can damage paint, so only use it where there is rust. Might be a good idea to tape up the surrounding area as I did when sanding.

Another option is to make an oxalic acid solution and dip a rag in it, then leave the rag on the rusted area. (Wear gloves.)

mgb, I used gaucho777's method on my son's Olmo. There was no way to match the colors so I used automotive Trim Black, which is a close match to the black brake cable housing.

Brad