Apply a generous amount of vinegar to a soft cloth. Scrub the rusty areas of the iron vigorously, re-applying vinegar to the cloth often. Allow the iron bed frame to soak in the vinegar for an hour. The vinegar will loosen the rust from the bed frame considerably.
Rinse the bed with water and scrub using steel wool. Repeat this process until the rust is removed and your iron is shiny.
Apply petroleum jelly to a paintbrush. Smear a thin layer of petroleum jelly to your iron bed, taking care to ensure application to the joints. Repeat this process annually to prevent rust from reappearing on your bed.