I purchased a hatchet today at a garage sale. It is sharp, the handle is comfortable, and the shoulder is snug in the eye. So what is the problem? The blade is very rusty. This is not actually a problem as it will let me try science!
Rust can be removed with elbow grease, chemical cleaner, or electrolysis. I am opting to remove it with electrolysis. The positive clip of a 12V car battery charger is attached to a piece of rebar and the negative clip is attached to copper wire wrapped around rusted tool. The rebar and rusted tool are then submerged for several hours in a solution of sodium carbonate and water (1 tbsp (15mL) per 1 gallon (3.8 L)of water).
Before pictures of the subjects. The chisel is from my late grandpa which has seen better days.
14 gauge copper wire wrapped around the tool.
Wood board keeps the wires separated.
The free ends are pigtailed. A ziptie keeps the rebar upright.
The positive terminal is connected to the sacrificial rebar. The negative terminal is connected to the copper wire.
The 12V battery charger is set to 2 amps.
After a few minutes black flakes form which are bits of rust being removed.
The car battery charger is plugged into a GFCI circuit. The electrolysis is also set up in a well ventilated area. A common science demonstration is using electrolysis to separate water into oxygen gas and hydrogen gas. I see no reason why this rust removing process would not also produce the gases.
Rust removing electrolysis is well detailed on Instructables.