I use elecytrolysis on rusty metal. All you need are a tub of water, some Washing Soda, a battery charger and an old piece of metal. Mix a couple tablespoons of washing soda in the tub of water (enough to cover the bar completely). Hook the black lead of the battery charger to the bar (doesn't matter if the black lead is under water). Hook the red lead to the piece of metal (make sure the red lead is not under the water). Make sure the metal and the bar are not touching. Plug in the battery charger and let it run. I do old hand planes this way, and it can take from 2 hours to overnight for really rusty stuff. After it's done then I use a 3M green pad to rub the rust right off, rinsing in hot water.
Tom