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.
Things You'll Need
Steel wool pads containing soap
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.