Does Rust-Oleum actually stop rust?

Yes, Rust-Oleum actually does stop rust when used correctly according to label instructions, though it does not magically eliminate existing deep rust without preparation. Rust-Oleum's rust-preventive formulations contain corrosion inhibitors, fish oil-derived resins, and pigments that seal metal from moisture and oxygen, which are the two elements that cause rust, thereby stopping further rust formation. Products like Rust-Oleum Rusty Metal Primer and Rust-Oleum Protective Enamel are designed to be applied over lightly rusted surfaces after removing loose rust with wire brush or sandpaper, and they penetrate remaining rust and create barrier that prevents moisture from reaching metal. Rust-Oleum Rust Reformer chemically converts iron oxide rust into a black inert substance that can be painted, effectively stopping rust chemically. Independent tests show Rust-Oleum provides good rust prevention for 5 to 10 years outdoors when properly prepped and topcoated. However, it will not stop rust if you paint over thick flaking rust without removing loose rust, or if you apply in wet conditions, or if surface has active water leak from overflowing gutters causing constant moisture. For best results, remove loose rust, clean surface, apply rust converter, then rusty metal primer, then two coats of protective enamel. If metal is severely pitted, rust may continue underneath. So yes, it stops rust when prep and application correct, but not if you just paint over heavy rust without prep.