How to Restore a Rusted Metal Door

Remove the door from its frame and set on an old tarp. Remove any hardware from the door, including the handle, locks, hinges and the metal plate near the doorknob. Take the hinges and locks apart, placing each component on the tarp.

Cover the hardware with a thin layer of petroleum jelly. Rub the hinges and locks with kerosene, wiping the kerosene over all areas. Both the kerosene and petroleum jelly stop the pieces from further rusting and add a protective layer to the pieces.

Wipe the metal door down with a degreaser, which cuts through any grease, oil or debris on the door, including oils from your skin. Rub an old rag over the door, removing any traces of the degreaser and taking away the rust particles.

Apply auto filler to any damaged areas, including holes or dents. Auto filler attaches to the metal and forces a near-permanent bond. Once the auto filler dries, sand down the surfaces with fine-grit sandpaper, until the filler sits even with the door.

Prime the door with a latex-based primer. Apply it with a paint roller or paintbrush, depending on your preference. Let the primer dry as long as the manufacturer recommends, which may take up to 24 hours. Wipe down the hardware with a dry cloth or rag and apply a coat of primer to those pieces, if you want them painted.

Pour the paint into a paint sprayer, which reduces streaking and gives the door an even look. Aim the sprayer at the door and apply a single, even coat. Apply a second coat, if desired. Paint the hardware with the paint sprayer and once dry, reattach the pieces to the door.