As Rust Bullet cures, it expels solvents and releases carbon dioxide gas while dehydrating the rust. The first coat of Rust Bullet soaks through the rust down to the metal below, encapsulates the rust and dehydrates it. As the first coat dries and gases off, tiny pin holes may form in the coating. The second coat is critical to fill any pin holes and seal the surface with an air-tight, armor-like shield of protection. If the pin holes are not sealed after the first coat, air and moisture may penetrate the coating exposing the surface to further damage. A two to three coat application typically achieves a DFT (dry film thickness) of the required 6 mils for general applications. Additional coats may be necessary to achieve the appropriate DFT for your project.