How does Mastercoat Permanent Rust Sealer compare to automotive epoxy primers?

Two coats of automotive epoxy primer, five coats of color, and two coats of clear will withstand 500 hours of salt spray. Two coats of Mastercoat Permanent Rust Sealer and one coat of AG111 Ultimate Finish Coating will do 14,000 hours of salt spray. Mastercoat Permanent Rust Sealer, if scratched, the rust will not go beyond the scratch. Epoxy primers are not air tight like Mastercoat Permanent Rust Sealer, so they are not very effective against rust, so rust will eat through it eventually.