Step 2 – Neutralizing Residual Rust
After having removed as much rust from the hole as possible, it is highly recommended to apply at least one coat of rust stopper. When applied correctly, this liquid will stop rust from spreading after the expanding foam and paint have closed the rust hole. When using the rust stopper, the solution must be allowed to dry before moving forward. Rust stopper liquids generally dry overnight, and you will know that the rust stopper has neutralized the rust if it has turned blackish. At this point, some like to apply a coat of primer on the neutralized rust for extra protection against possible future rot spreading.