To remove rust from small parts, I connect them to the negative lead of a non-automatic battery charger and place it in a bucket of water with another sacraficial piece of steel attached to the positive lead. Then, I add Arm and Hammer washing soda until it starts to bubble. Let it sit for a while and you're done. The tools with a light coat of rust will be stripped clean and the heavy stuff will be converted to a black substance that doesn't spread like rust anymore. I believe it's a similar reaction to what occurs when you use a chemical like rust seal.