Prevent steel milk pails from rusting by completely drying them after use, limiting their exposure to salt water and storing them in a dry location. If the pails are decorative and are not used to collect and transport milk or other consumable liquids, consider coating them with paint, wax, proprietary rust prevention products or homemade solutions to prevent rust before it can begin to damage the steel.
Rust occurs because iron, the primary element in steel, readily reacts with oxygen in the atmosphere to produce iron oxides. Iron oxides are the flaky, reddish-brown chemical products that result from the chemical reaction between iron and oxygen.
While all steel in contact with the air rusts eventually, the chemical reaction proceeds much more quickly in the presence of water, which is why wet steel rusts more rapidly than the dry alloy. Salt greatly increases the rate at which rust forms, as it is a strong electrolyte and improves water's ability to conduct electricity. Even milk, which contains dissolved electrolytes such as calcium ions, can increase rust formation this way.
The most effective way to prevent rust from forming on milk pails or any other steel item is to completely coat the surface of the metal. Coating steel with paint, wax or a natural substance such as lanolin prevents rust by separating the steel's surface from the atmosphere. However, because many paints and waxes are not safe for human consumption, they cannot be used on milk pails that are in active use.