Rust-Oleum Stops Rust Primers provide a sound base for applying Stops Rust enamels on heavily rusted steel. Primers provide twice the rust prevention than using enamels alone. Using primers promotes topcoat adhesion and helps prevent chipping, cracking, and peeling. In addition, using Stops Rust primers eliminates the need for multiple coats of the enamel finish. Not for use on galvanized steel.