Bondo can be used in conjunction with fiberglass mats to cover a rust hole
Bondo is a body filler produced by 3M that you can use to fill in rust holes or damaged sheetmetal. It is a thick plastic paste that is spread over the affected area, then sanded down to a smooth finish. Bondo cannot fill a open hole on its own. To fill a rust hole, you will need to repair the surface prior to bondo application. This can be done either by spot-welding in fresh metal, or using fiberglass mats.
Instructions
1. Clean the repair area with soapy water and let it dry, Use a metal wire brush to scrub the area you want to fix. You need to remove all the existing rust, dirt and debris. Use 220 grit sandpaper to scuff the area to assure adhesion. Use a hammer to gently tap inward the edges of the hole, then spray the area with rust inhibiting primer. Allow an hour or more for the primer to dry. Sand down the primer so that it is smooth.
2. Patch the rust hole. You have two choices here: Have a shop weld in a piece of metal, or use a fiberglass mat and resin. Let's assume you will use a fiberglass mat because it is easier and does not require access to a welding machine. Mix the hardener and resin from the fiberglass mat kit in the kit's tray. While the exact formula varies by kit, you will typically want to mix 12 drops of hardener for every ounce of resin you use. Cut a piece of fiberglass mat that is about 50% larger than the hole, then soak it in the resin.
3. Wet the surface of the hole with resin, then place the mat onto the hole. Use a brush to smooth the patch and remove any air bubbles. Brush a coat of resin over the patch, then apply a second fiberglass mat. Allow it to dry for two hours. Sand the dried patch with sandpaper lightly with 80 grit sandpaper.
4. Place some bondo on a piece of cardboard and mix in the supplied catalyst. Mix the two together until it is uniform in color. Using a plastic spreader, spread the bondo onto the repair area over the fiberglass mat. Allow the bondo to dry, then sandit smooth with 80-grit sandpaper.
5. Wipe the surface clean, then spray primer onto the bondo area. Once the primer is dry, spray your topcoat of paint.
Tags: rust hole, area with, fiberglass Allow, fiberglass mats, fill rust
