How does Mastercoat Permanent Rust Sealer compare to other paint over rust products?

Mastercoat Permanent Rust Sealer is sunlight stable, sandable, paintable, sticks to clean steel, and is air tight. We don’t recommend painting just black urethane or just clear urethane over rust since these coatings are not air tight and are simply polyurethane designed for wood and concrete. Mastercoat Chassis Black Finish Coating is ideal over Mastercoat Permanent Rust Sealer on a chassis and on floorpans, especially with a paint brush, but not as a rust sealer alone. Mastercoat Chassis Black Finish Coating can seal rust and prevent from coming back it for a few years, but you'll get a much longer service life if you use Mastercoat Permanent Rust Sealer as a primer and Mastercoat Chassis Black Finish Coating as a topcoat.