I have a cheap tool with some rust on it. It's probably cheaper to buy a new one than to clean it. But I wonder if is there any solution where I can drop it and retrieve it clean. Is there anything like a rust solvent?
Perhaps naval jelly would (Phosphoric acid) do the trick? Or maybe electrolysis…
This stuff is sick: http://www.evapo-rust.com/
I used it on a drill press my buddy left out on a patio in the rain for a year. Virtually no scrubbing. I don't understand how this is not one of the most widely known products in the world. It is THAT good. I guess with the military as a client, they don't need the business from the public. Here are some pics. Truly an amazing product. I purchased a gallon of it at a Harbor Freight store for $20.
I use CLR for that sort of thing. The main purpose in my house is for hardwater scale, which accumulates on everything, but it also works on rust. Handle with care, it is wicked strong.
In Brazil we have Semorin - Tira Ferrugem (rust remover)
SUPER EASY!!! Get a cheap nail brush (but a big one for use on feet is better, if you're willing to sacrifice it), toss your tools in a tall cup of baking soda (don't measure, dump in as much as you think you need and a little more) with some water. Take out one piece at a time and go to town scrubbing on top of a good hand towel. Keep going until it's as clean as you need it to be.
1 part molasses to 8 parts water. soak for one week. it works like a miracle. I got some old rusted out drill bits at a flea market. I mean really rusted out. After this treatment I could read the size markings on the bits.
It used to be that pepsi and/or coke would eat away rust - not sure if the newer formulations will still to that, though. You could also try some vinegar.