The Rust-Oleum Stops Rust 12 oz. Automotive Primer Spray has a fast-drying, rust-preventative formula. Suitable for use on a variety of materials except-galvanized metals, this primer spray has both indoor and outdoor durability. Featuring a light-gray color, this primer spray works well under most automotive paints. To use, spray on and wait 15 minutes before applying a top coat or wet-sand to achieve an ultra-smooth finish.