cg1985

So I have this Peugeot that I am going to restore (yea, yea I know, don't bother laughing at me about finding french parts!).

It has some minor rust, so I mixed about 3 tablespoons or so of oxalic acid into about a quart and a half of warm water, I then soaked paper towels in it, and wrapped them around the bike.

I did this on recommendation of a bike restorer near where I live. But I didn't ask enough questions.

First, off, is that an OK mixture? should it be more, or less concentrated.

Assuming the mixture is OK, how long should I let it sit and soak?

BCRider

I think you'd have been better off with a more concentrated solution but if it's working then fine. But instead of just letting it sit I've vigoroustly rubbed it with a rag or something else non abrasive on painted surfaces. If the solution is sufficiently strong this will pretty much remove the rust as quickly as solvent and scrubbing removes a stubborn tar stain. There shouldn't need to be a long soaking period. Or at least certainly no longer than a few minutes.

One the rust is gone and after a good rinse and dry you may be able to see the little pores in the paint where it bloomed out. Regardless of if you can see them or not the area should be sealed with something like a couple of coats of Danish oil or boiled linseed oil. These products are used with a wipe on/let soak/wipe off action so it soaks down into the pores and seals the rust. These types of oils dry after a while so they don't allow dust and grit to stick to them but you don't want to leave it on the outside of the finish since they do stay sticky for a while. A couple of applications wiped on and then the excess wiped off will be more than enough to soak in and coat the rust spots and seal them off from further problems.

cg1985

Thanks for the suggestion!

I had heard of a cleaner called, "zud" which contains Oxalic Acid, if this doesn't work, I'll pick some of that up, get a toothbrush and make a paste with it. Then try scrubbing it off.

BCRider

Zud, hey? My own supply of oxalic comes as a cleaner called Bar Keeper's Friend.

Assuming you still have some of the pure oxalic left over why not try the toothbrush slurry mix trick with it? Oxalic acid is not a highly corrosive acid such as hydrochoric and sulphuric so while I would not want to brush my teeth with it or get any in my eyes a toothbrush's worth used with some rubber dispoable gloves and safety glasses isn't going to hurt the paint on the frame at all.

cg1985

Unfortunately, the oxalic acid is all used up in my highly dissolved mix.

Well, my soak method helped remove some of the rust stains, and a little bit of the rust, but I think I need a higher concentration to really get it off.

I am going to go to the hardware store and see if I can pick up some barkeepers friend or Zud.