Using Foam Glue to Repair Rust Holes in Cars?
2 Answers
It is not recommended to use foam glue for repairs as water can still accumulate inside and cause rusting; rust on the rocker panels is common in older vehicles and usually starts from the inside. Use a steel wool pad or sandpaper to remove the paint from the rusted area, then decide whether to repair or replace the entire panel based on the severity of the rust. If the rust is not severe, start by using very fine wet sandpaper dipped in water to gently sand away the rust spots. After completely cleaning the area, apply a layer of primer to prevent the rust from spreading. Once the primer has dried, use wet sandpaper to smooth the surface, then proceed with color matching using a touch-up pen or spray paint. If the rust has caused small holes, you can cut thin aluminum sheets into the shape of the hole and layer them over it as needed. Then apply filler and paint.
Back when I was helping out at the auto repair shop, car owners often asked if they could use foam sealant to patch rust holes. Honestly, this method doesn't work. Foam sealant is designed for insulation and gap filling, like around doors and windows—it lacks sufficient adhesion and hardness. On rusted car body sections, rust holes indicate underlying metal corrosion. After applying foam sealant, it quickly absorbs moisture, expands unevenly, and actually accelerates corrosion spread. Even worse, when the car body bears pressure, the foam sealant cracks under stress, reducing structural strength. In case of an accident, there's zero protective function left. The safest approach is still to have a professional weld the patch or use automotive body panel adhesive. It may cost more, but it's worth it. Regular inspections of the paint protective layer are also crucial—address small rust holes early to avoid major repairs.
