Using a stiff bristled brush, clean off any loose rust, peeling paint, dirt and debris from the lawn chairs. Wipe the chairs down with a soapy rag and air dry completely.
Spray or brush on Rust Doctor latex paint. This paint will turn black as it turns the rust to magnetite. Make sure the Rust Doctor is sprayed into all adjoining joints and that it completely covers any bolts or screws that connect pieces together. Turn the chairs over to make sure that they are evenly coated on top and bottom with Rust Doctor. A second coating of Rust Doctor can be applied while the original coat is still tacky; do this if you find any of the rust still showing after the first application.
Allow the Rust Doctor latex paint to cure for 24 hours. Apply semi-gloss spray paint in your desired color according to the manufacturer's directions. A second coating is only necessary if the first coat didn't provide complete coverage. Most spray paints are dry to the touch within 30 minutes of applying; your lawn chairs should be completely cured after 24 hours and ready for use.