The process of rust proofing a metal fire pit depends on which metal the pit bowl and stand are made from. Usually store purchased copper and steel fire pits sport rust proof paints and coatings as part of the manufacturing process. If the homeowner makes his own fire pit, however, rust proofing must be the final step of the home fabrication process. Paints, silicone coatings and oils are all viable choices for use alone or in tandem to keep rust at bay and maintain a gorgeous fire feature.
Identify the type of metal the fire bowl and any stand for the bowl are made of, and purchase a weatherproof spray paint made to adhere to that type of metal.
Empty the fire bowl, and clean the bowl and stand with a degreasing dish soap or shampoo and water. Dry all the metal thoroughly with a towel, paying special attention to joints, corners and screws/screw holes.
Spray the inside and outside of the metal fire bowl and all the metal of any stand with the weatherproof spray paint of an appropriate colour or colours, and allow the paint to dry according to the manufacturer's instructions.
Coat the outside, including the bottom, of the metal fire bowl, and the metal of any stand with a petroleum-based weatherproofing oil by wiping a thin layer of the oil onto the metal with a soft cloth. Repeat this step every few months.
Cover the metal fire pit with a vinyl cover manufactured to fit snugly around the top and sides of the metal fire bowl to help keep rust-causing moisture from developing and sitting on the metal when the fire pit is not in use.
Watch for rust formation in unexpected places, which may indicate the very beginning of a bigger developing rust problem. Places such as joints, corners, around screws and screw heads themselves under the feet of any stand, and the very bottom of the metal bowl are all places where rust can develop yet be missed if the homeowner is not looking for it.