Everyone (:-)) knows the vinegar/table salt trick to make dilute buffered HCl for derusting, but I read about a new recipe - two parts 5% vinegar and 1 part 3% hydrogen peroxide. This will make a very dilute (about 1%) solution of peracetic acid, which will have a sharp odor so don't stick your nose in it! Besides being used to kill algae in ponds (diluted to about 10-50 ppm in the pond) it turns out it does a great job of making brass look new again after machining or heating. Make enough mix to submerge the brass, and wait overnight - voila! Also strips copper sheet clean after I blackened it with a torch, but didn't do a thing for oxidized 304SS. Don't know about rust on iron but I bet the salt would be better for that since the peracetic acid will be consumed pretty fast. It is a little slow since it is so dilute, but works great. I'm not really sure if the slow step is the formation of the peracetic acid or the cleaning of the metal. Maybe one day I'll do some experiments where I mix one batch and let it sit for an hour before adding metal while in a duplicate batch I dump everything together at the start, and even try adding some salt, or maybe not :-). Can't remember where on the Internet I saw this, so can't give the proper attribution, sorry.
Don't drink it, or soak your hands in it, and especially DO NOT get it in your eyes. It wants to glue your eyelids to the eyeballs and no one wants that. That's the high points off an MSDS for some 15-20% stuff. I really don't know how nasty this dilute stuff is so be adult about it.
-- Regards, Carl Ijames carl dott ijames aat verizon dott net (remove nospm or make the obvious changes before replying)