ToolNut put together a nice guide for using electrolysis to clean up rusty tools:
This is a relatively simple, safe and cheap way to remove light or heavy rust from any ferrous object. I used this process to restore an old wood plane that I bought for $1 (it looked totally un-usable because of the rust). As opposed to grinding, heavy wire brushing and acid bath processes, this method removes none of the original steel and is not noisy or caustic.
I’m going to clean up a few tools in the basement that haven’t been taken care of as well as they should have… too bad none of them are as sweet as that plane ToolNut came across for a buck.
Electrolytic Rust Removal aka Magic – Link