How do you remove rust from old tools?

We have old tools that were my dads that were in their basement and the basement gets water in it when it floods so these tools got rusty.

Phosphoric acid will change rust to black iron. Look for a product in home supply stores called Naval Jelly. It's a jelly with phosphoric acid. Clean the rust off best you can with a wire brush and/or a grinder and apply a generous coating of the jelly. In about 30 minutes the rust will be gone.

Note that cleaning off the loose rust is critical because any of it the jelly doesn't contact won't make the change.