The Rust-Oleum Stops Rust 32 oz. Clean Metal Flat Rust Preventive Primer is designed for use on lightly rusted metals and works well on bare and previously painted metals. This primer can be used both indoors and outdoors and provides coverage for up to 100 sq. ft. To use, apply directly over the rust to provide great adhesion for finishes. The primer dries in approximately 120 minutes.