Scrub all the surfaces of the furniture to get rid of rust and flaking paint, using a steel wire brush. If you see areas where the paint has bubbled, rust is under the paint. Use a screwdriver to break through the paint and scrub with the wire brush. You may need to use a coarse file to remove rust from heavily-damaged areas.
Spray the furniture with a rust remover to get rid of rust you may have missed. Wear your protective gear (heavy gloves, goggles, and a respirator).
Sand the surfaces lightly with a fine-grit sandpaper.
Apply a coat of oil-based clean metal primer and let it dry according to the manufacturer's instructions. Wear your protective gear for this step. Clean your brush with the appropriate solvent and rags.
Paint or spray with rust-resistant paint. Follow the manufacturer's directions for how many coats you should apply and what the drying time between coats is. Wear protective gear when you are applying the paint, which probably contains toxic solvents. Clean your brush with the appropriate solvent and rags.