Things You'll Need
Steel wool pads containing soap
When iron and steel are exposed to water and oxygen, they begin to rust. Rust is a chemical compound called iron oxide. Iron oxide molecules are larger than the molecules in iron and steel; the larger molecule size results in rust bubbling out from the metal and flaking. There are many petroleum- and wax-based products on the market that prevent rust; zinc primers available in aerosol cans will also prevent metal from rusting. Once you remove the rust from your milk crates, treat them with a rust-prevention product and keep them dry.
Dip the steel wool pad in water to moisten.
Rub the rusted area with the pad, using quick back-and-forth movements.
Wipe with the damp towel to remove the rust residue and soap.
Sand off the remaining rust with the fine-grit sandpaper, using the same quick back-and-forth motion.
Wipe the crate clean with the damp towel; rinse it often.
Dry the crate thoroughly with a towel, or let it sit in the sun until it's completely dry.
If you are going to paint your metal crates, prime them first with a metal primer that prevents rust.
Wear gloves when working with steel wool to avoid skin abrasions.