Rust, or iron oxide, is formed when iron reacts with water and oxygen, changing the metal into rust that flakes into a powder. Although most people try to keep their iron and steel objects from rusting, rust powder can be a useful material for some projects. It's possible to visit a junkyard to rub rust off old cars with steel wool, but you can actually make it at home through the process of electrolysis.
Place the bucket and batter charger in a well-ventilated area. Good locations include outdoors, under an awning, or in a shop with an open door and fans.
Attach the two steel pieces to the positive and negative clips of the battery charger. Place them in the plastic bucket. There should be enough room in the bucket so that the steel pieces don't touch.
Fill the bucket with water and then plug in and turn on the battery charger.
Add salt to the water. Stir the salt in with a wooden stick or spoon. As you add the salt, watch the amp level displayed on the battery charger screen. When the screen reads two amperes, stop adding salt.
Turn on the fan and open a door if you are in a shop. While the electrolysis takes place, fumes will be released from the bucket. Do not permit open flames in the area.
Let the metal oxidize for up to 12 hours, or until the steel bars have completely corroded. You may want to check the bars from time to time to judge how much metal is turning to rust. You may stop the process at any time by turning off the battery charger and removing the clips from the bucket.
Lay the cloth over the wire mesh, with the wire placed on top of another plastic bucket. Stir up the rust sludge in the electrolysis bucket and slowly pour the contents over the cloth.
Leave the cloth out in the sun to dry naturally. If the rust is still a sludge, you may wish to scoop it onto a plate or tray and put the tray into a warm oven for several minutes to dry. Scrape the rust off the tray after baking and store in a covered container.
Place steel balls or marbles into the container and shut the lid. Shake the container vigorously for several minutes. Check periodically to see when the rust has turned to a powder. When ready, dump the contents onto a sheet of paper, pull out the steel balls and collect the rust powder.