Fill a spray bottle with a de-greasing, ammonia-based cleaner. Apply it to the chair and wipe the metal with clean, dry rags.
Scrub any rusted portions with a steel bristled brush to remove as much rust as possible. Apply firm pressure and move the brush back and forth with a quick motion.
Sand the chair to remove all remaining rust. Go over the areas that you cleaned with the steel bristled brush and remove all small rust particles that remain. Sand the rest of the chair lightly to scuff the surface and prepare for paint.
Fill any holes with putty designed for metal applications. Scrape it into the hole with a metal scraper, wiping across the surface to make it as smooth as possible. Allow it to dry completely. Sand to remove any residual putty. Wipe away sanding dust with a damp rag.
Prime the chair with a bonding primer. Choose one in a spray can for the most even application. You can paint the chair with a brush but the process will take longer and will produce a less perfect finish. Move the primer in a steady back and forth motion to completely cover the surface. Allow the first coat to dry completely. Add a second coat if you can still see the original surface beneath the primer.
Paint the chair with spray paint. Choose a paint for metal surfaces that will help to prevent rust. Start at the top of the chair and work downward. Apply 3 to 4 very thin coats, allowing each to dry before applying the next. Allow the final coat to dry overnight.