Here is a neat trick to clean your old and rusted tools or other metallic objects without any effort. Electrolysis is the name. A jar with water and plenty of electrolyte (like salt) is used to submerge the piece-to-be-cleaned. The negative of the supply is connected to this piece. On the other side a piece of iron is submerged with the positive pole of the power supply connected to. This piece of metal will be severely punished, so make sure that it comes from your scrap bin. Now power up and let it run for a couple of hours. Clean with water and soap and voila!