How To Use Expanding Foam To Re-Build Your Car
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.
Step 3 – Filling with Expanding Foam
If the primer coat that was first applied is dry, the hole can be filled with the expanding foam. This process might require cardboard supports to keep the liquid foam inside the hole to be filled. The foam should be applied so that it not only fills the hole but overfills it. The reason for overfilling the hole is because the excess foam will be cut away after it dries. This excess expanding foam is what allows shaping the surface that body filler will be applied to.