Scrub the rusted portions of the bed with a steel bristled brush. Remove as much rust from the bed as possible.
Fill a spray bottle with phosphoric acid. Spray the wrought iron with the acid. Allow the chemicals to penetrate overnight. The acid will turn any remaining rust into a crust of iron phosphate. Scrub away the crust with the steel-bristled brush.
Dip a sponge into a mixture of dishwashing soap and warm water. Clean the chemicals from the iron. Wipe away the soap with clean water.
Sand the surface of the iron with medium grit sandpaper. Lightly scuff the iron to create texture. The primer will sink into the grooves and better adhere to the iron surface. Wipe away any sanding dust with a damp rag.
Prime the iron bed with a bonding primer. Choose a primer formulated for metal surfaces. Apply the primer in a thin, even coat. Primer will help create a smooth base for the paint and will also prevent the color from bleeding through the paint.
Dip a medium sized paintbrush into the gold paint and apply a thin layer to the iron bed. Use an acrylic paint for the best adhesion. Allow the first coat to dry. Apply two to three additional coats.
Apply one to two coats of polyurethane to the bed with a clean paintbrush. Allow each coat to dry to the touch before applying the next. Let the final coat dry overnight.