half gallon mason jars with rust stains

a freind of mine gave me 12 half gallon mason jars that had pool shock stored in them. the lids where on tight and rusted through. pool shock when down the toilet as I live in the city. I have washed the jars thoughly with very hot water and a bottle brush but the stains will not come off  even with heavy scrubbing.

Any ideas on what to use these jars for with rust stains?

Any ideas on how to remove the rust stains. I am curious what gasoline will do. my dad has a rust remover solovent.

Gasoline will do nothing. What you need is something that chemically breaks up rust. Any light acid will do it, including vinegar. I'd soak them in a vinegar, the stronger the better. When I need something stronger, I use a type of light acid called Calcium, Lime and Rust remover, it's very similar chemically to strong vinegar. Be safe with acids stronger than vinegar, use gloves and eye covering, it's not something to get sloppy with.

Since it sounds like the main stains are on the top, where the lids rotted, I'd put them in a chemical safe container, (plastic trash can would work well) head down, and pour a whole big bottle of cheap vinegar in there. Don't add water if there's any way you can help it. You may have to do them in batches. Move them, roll them around for a few days, then see if they scrub up. You can put the next batch into the same vinegar.

Soda pop removes rust too. It contains citric acid.