Tool and Material Checklist:
Corrosion damage on a car takes two forms: surface rust and rustouts. In its early stages, surface rust is a reddish coating on the metal. In time, the rust eats pits into the surface. These pits eventually develop into holes, or rustouts. Each type of damage requires a special repair procedure, both of which are covered in this booklet. When doing the procedures, do not skip any steps-there are no shortcuts to good auto body work.
Areas affected by light surface rust can be re- paired simply by grinding the rust away and applying a coat of metal conditioner. If the metal is pitted, however, additional steps are needed.
Preparing the Surface
1. Wash the affected area with water and mild detergent, then clean with a wax and grease remover.
2. Apply masking tape to the surrounding trim to protect it when grinding.
3. Use a hand sander or scraper and #36 or #80 grit paper, or a lightweight air grinder and #24 grit rigid sanding disc to remove the surface rust. Hold the grinder against the car at a 10o angle and use a back and forth crosscutting action. When moving the grinder to the right, press the upper left corner of the disc against the metal; when moving to the left, put the pressure on the upper right corner.
NOTE: Always wear safety glasses or goggles when grinding. To avoid breathing paint and sanding dust, an air filtering mask should be worn.
4. If necessary, use hand tools or a die grinder attachment to remove rust from the pits, panel edges, and other hard-to-reach areas.
5. Use metal conditioner to etch the surface and improve the bond between the metal and the primer. It must be diluted before using; follow the manufacturer's instructions.
6. Apply the metal conditioner with a clean cloth and use a separate cloth to wipe it off before it dries, If the conditioner dries before it can be re- moved, rewet the panel and wipe it dry.
NOTE: Always wear safety glasses or goggles and chemically impervious gloves when handling metal conditioner or rust deactivator.
1. To prepare the filter, first place the required amount of resin on a mixing board.
2. Knead the tube of hardener thoroughly, then squeeze a narrow ribbon across the glob of resin. This will provide the correct proportion of resin to hardener.
3, Mix the resin and hardener with a plastic spreader, using a firm, flat wiping motion. Do not stir; this will trap air in the filler and form pinholes.
4. The filler will begin to harden after a few minutes. Use the following table to determine how much working time you will have.
5. Continue mixing until the filler is a uniform color. Use the color guide on the package to judge the accuracy of the mixture. If it is too light, add more hardener; if it is too dark, add more resin.
6. Scoop up some of the filler onto the edge of the spreader and spread a thin skim coat over the pitted area. Use moderate pressure to force it into the pits.
7. Allow the filler to harden, then block sand with #80 grit sandpaper until the filler becomes level with the metal. Use compressed air to blow away any excess filler dust.
NOTE: Always wear safety glasses or goggles when blowing with compressed air.
8. If necessary, apply another skim coat of filler. Wait until the filler has dried completely before proceeding.
Sanding and Priming
1. Final sanding and priming are important to achieve a smooth, professional-looking finish. Begin by wet sanding with #400 grit sandpaper and a sanding block. Use long, straight strokes to avoid creating low spots.
2. Clean the sanded surface with a tack cloth, and dry thoroughly.
3. Spray primer over the repair area and several inches of the old finish around it. Allow the primer to flash (surface dry) for five minutes.
NOTE: Always wear safety glasses or goggles and an air filtering mask when spraying primer or paint.
4. Wet sand lightly with #240 grit sandpaper, then clean and prime once or twice more. Between coats, wet sand lightly with #400 or #600 grit sand- paper to achieve a very smooth surface.
Spots of surface rust can be a sign that rust has eaten through from the backside of the panel. Re- pair small rustouts immediately before they be- come bigger problems.
Preparing the Surface
1. Grind the repair area with hand tools and #36 or #80 grit paper, or use a lightweight air grinder and #24 grit rigid sanding disc.
2. Use a pick hammer to bevel the edges of the rustout. This will remove any loose rust and paint, as well as create a depression to prevent the filler from falling through the hole.
3. If the backside of the panel is accessible, use a wire brush or scraper to remove accumulated dirt and undercoating.
4. Apply a rust deactivator to the rust to seal out air and moisture and prevent further oxidation.
5. Apply metal conditioner to the bare metal.
1. Plug all rust holes with waterproof, fiberglass- reinforced filler. (Regular plastic fillers absorb moisture and should not be used.) Use a plastic spreader to work the filler into the holes.
2. Allow the filler to harden, then sand smooth. Wipe away excess dust with a clean cloth.
3. Cover the holes with a layer of regular plastic filler.
4. After the plastic turns rubbery but before it hardens, knock off the high spots with a cheese grater. Hold the grater at a 10° to 20° angle to the surface and pull it across the repair area.
5. When the filler has completely hardened, sand it down, level with the metal. It is now ready to be finish sanded and primed as described earlier.
Rust on the underside of a panel is not usually noticed until it has attacked a large area of metal. If left unattended, the rust will spread until it has eaten a gaping hole in your car. Large rustouts are not only unattractive, they can also affect the structural integrity of a vehicle. Structural members with large rustouts should either be re- placed entirely or the rusted area cut away and new metal installed, Of course, the age or overall condition of your car might not warrant these more expensive repairs, so this procedure uses a relatively inexpensive fiberglass cloth patch and resin liquid.
Preparing the Surface
1. Cover all surrounding trim pieces with masking tape to protect them when grinding.
2. Use hand tools and #24, #36, or #80 grit paper, or a lightweight air grinder and #24 or #36 grit rigid sanding disc to remove as much loose paint and rust as possible.
NOTE: Use extreme care when grinding a rust- out. Because rust deteriorates a panel until it is very thin and weak, excessive pressure with the grinder can burn a hole right through the metal. Always wear safety glasses or goggles when grinding.
3. Use a hammer or tin snips to break away the softened metal around the rustout. Hammer down the edges of the hole slightly to bevel them.
4. Use a hand sander or a #50 grit rigid sanding disc to remove surface rust. A wire brush or die grinding attachment is ideal for cleaning out pitted areas.
5. Apply metal conditioner or a rust deactivator to the repair area to neutralize any remaining rust, particularly along the edges and in the pits.
6. After cleaning the backside with a wire brush or scraper, apply a rust deactivator. A solid black coating should develop. If the color is splotchy and uneven, apply additional coats of rust deactivator, waiting one to two hours between coats.
WARNING: If any excess rust deactivator runs onto the car's finish, wipe It off Immediately using a cloth dampened with white mineral spirits.
Applying the Patch
1. Cut a piece of fiberglass cloth approximately 2" larger than the hole. Cut a similar piece of plastic film, or release paper, approximately 4" larger than the hole.
2. If a stronger patch is desired, make a laminate by cutting additional layers of fiberglass cloth. Each additional layer should be 1/2" smaller than the preceding one.
3. To provide maximum strength, use either liquid resin or a fiberglass-reinforced filler with long strands. Prepare the filler as described earlier, making sure it is mixed thoroughly before applying.
4. Spread a thin coat of filler on the repair area and on the piece of plastic.
5. Place the fiberglass cloth on top of the filler- covered piece of plastic. If additional layers are being used, set the smallest one on first, the next largest, and so on; the largest piece is put on last because it will be the bottom of the patch.
6. Place the patch, fiberglass side down, over the hole. Use a plastic spreader to smooth out any wrinkles or high spots in the plastic and press out all air bubbles.
7. When passing the spreader over the center of the rustout, press down hard enough to leave a 1/8" to 1/4" indentation. Do not press so hard that filler is forced out from beneath the patch.
8. Use the spreader to feather the edges of the patch level with the surrounding metal.
9. Let the patch cure, then remove the plastic. While the filler is still rubbery, file down any high spots with a cheese grater.
Completing the Repair
1. Mix enough fiberglass-reinforced filler to fill the 1/8' to 1/4" indentation in the patch. Use the spreader to apply the filler evenly and press hard enough to force out air bubbles. Always work the spreader from the edges to the center.
NOTE: A smoother application can be achieved by placing a piece of plastic film over the filler first, then working the spreader over the plastic.
2. Let the filler dry, then remove the plastic film (if used). Sand with #50 grit sandpaper and a sanding block to within 1/16" of the finish.
3. Switch to #80 grit sandpaper and sand down to the finish. Do not over-sand this will only create low spots that require additional filler.
4. Feather the edges of the filler level with the surrounding surfaces.
5. Wipe the repair area with a tack cloth and use compressed air to remove any excess dust particles. Spray with primer.
6. When the primer has completely dried, coat the repair with glazing putty. Use a clear rubber squeegee to apply the putty in smooth strokes.
7. When the putty has completely dried, use #240 grit sandpaper and a sanding block to smooth the glazed surface. Fill any remaining pin- holes or voids with putty, then sand again.
8. Wet sand lightly with #400 grit sandpaper to remove any sanding scratches.
9. Clean with a tack cloth, then prime the repair area again. When the primer has dried, the repair is ready to be painted.