The best way to repair rusty wrought iron railings is to remove all of the rust, prime the railing with a good quality primer, and then paint it with a good quality paint. Make sure that you use a paint or primer that is designed for metal surfaces, and follow the manufacturer's instructions carefully.

You can repair rusty wrought iron railings by using a wire brush to remove the rust, and then cleaning the railing with a degreaser. Next, you should apply a primer to the railing, and then paint it with a rust-resistant paint. Finally, you should seal the paint with a clear coat of sealant.