Electrolysis rust removal: a bucket, a battery charger and a sacrificial rebar

The gentlest way to strip rust off old hand planes, wrenches and cast iron. No grinding, no pitting beyond what the rust already did.

Setup

• 5 gallon bucket of water with a tablespoon of washing soda (sodium carbonate, not baking soda) per gallon.
• A piece of rebar or scrap steel as the anode, clipped to the positive lead.
• Your rusty part hung in the water from the negative lead. Do not let them touch.
• A manual (not "smart") battery charger on the 2 to 10 amp setting. Smart chargers refuse to work because they do not see a battery.

Run it

Bubbles mean it is working. A few hours for light rust, overnight for heavy. The water turns disgusting; that is normal. Pull the part, scrub with a brass brush under running water, dry immediately and oil it or it flash-rusts in minutes.

Safety

It makes hydrogen. Do it outside or in a garage with the door open. Do not use stainless steel as the anode; it makes toxic chromium compounds.