Removing minor scratches on the body
If the scratch is superficial and does not reach the metal of the body, the repair is very simple. Lightly rub the area of the scratch with a refinishing agent or a very fine abrasive paste to remove the flaking paint from the scratch and clean the surrounding area of the body from the mastic. Rinse the area with clean water.
Apply car enamel to the scratch with a small brush. Continue applying thin coats of enamel until the surface of the enamel in the scratch is level with the surrounding paintwork. Allow the new enamel to cure at least two weeks, and then make a smooth transition with the surrounding paintwork by rubbing the paintwork in the area of the scratch with a refinishing agent or a very fine abrasive paste. And finally, apply polishing mastic.
In places where the scratch has reached the metal of the body, causing it to corrode, a different repair technique is required. Use a penknife to remove any loose rust from «bottom» scratches and apply anti-corrosion paint to prevent future rust. Using a rubber or nylon spatula, fill the scratch with an appropriate putty such as «bodystopper». If necessary, this putty can be mixed with a thinner for nitro enamels, obtaining a very thin paste, which is ideal for filling narrow scratches. Before the putty in the scratch hardens, wrap a piece of smooth cotton rag around your finger, dip your finger into the nitro thinner and quickly run it over the surface of the putty in the scratch. This will create a slight indentation on the surface of the putty. Now the scratch area can be painted as described above in this paragraph.
Body dent repair
If there are deep dents on the bodywork, the first task is to straighten the dent to such an extent that the damaged area of the bodywork approaches its original shape. There is a small nuance in trying to completely restore the original form. Since the metal in the damaged area is stretched upon impact, it cannot fully return to its original contour. It is better to ensure that the level of the dent is located approximately 3 mm below the level of the adjacent body area. In cases where the dent is very shallow, you should not even try to straighten the body. If the reverse side of the dent is accessible, it can be gently «earn some money» mallet with a wooden or plastic head. At the same time, firmly press a block of wood against the outside of the panel to absorb the energy of the mallet and prevent it from «swell» large area of the body.
If the dent is in an area of the body that is double-skinned, or there are other reasons preventing access from the inside, a different technique is applied. Drill a few small through holes within the damaged area - especially in the deeper area of the dent. Then drive the long self-tapping screws into the holes just enough to get a good grip on the metal. Now the dent can be straightened out by pulling the screws by the heads with pliers.
The next stage of repair is the removal of paint from the damaged area and in the area at a distance of 2-3 cm from it. This is most easily done with a wire brush or emery wheel and an electric drill. But this can be effectively done by hand with sandpaper. To complete preparation for applying putty, scratch the bare metal surface with a screwdriver or file shank, or alternatively drill small holes in the area to be repaired. This will ensure better adhesion of the putty to the body.
To complete the repair, refer to the paragraph on applying filler and spraying primer and enamel.
Repair of holes resulting from corrosion or holes
Using an emery wheel or a wire brush and an electric drill, completely remove the paintwork in the repaired area and at a distance of 2-3 cm from it. In the absence of an electric drill with a brush, a few sheets of sandpaper will help to do this job no less efficiently. Once the paint is removed, you can assess the severity of the corrosion and decide whether to replace the entire panel (if it is possible) or repair the damaged area. New body panels are not as expensive as most people think. Installing a new panel is often faster and more acceptable than attempting to repair large corroded areas.
Remove all additional elements from the damaged area, with the exception of those that will act as guides when giving the original shape to the damaged area of the body. Then, using metal shears or a hacksaw blade, remove «weakened» and other parts of metal, strongly «eaten» corrosion. While tapping around the perimeter of the hole with a hammer, slightly fold the edges of the hole inward to create a small indentation for the putty.
Use a wire brush to clean the area to be repaired of «rashes» rust on the surface of the remaining metal. Apply anti-corrosion paint to this area. If the back of the rusted area is accessible, treat it in the same way.
Before applying the putty, you will need to plug the hole in some way. This can be done with aluminum or plastic mesh or aluminum foil.
For larger holes, the best material is aluminum or plastic mesh or fiberglass. Cut a piece approximately the size of the hole and place it over the hole so that its edges are below the level of the painted surface of the body. The patch can be fixed with a few drops of putty around the perimeter.
For small or very narrow openings, aluminum tape should be used. Unwind a piece from the roll and roughly cut it to the desired size and shape. Peel off the paper layer (if available) and cover the hole with tape. If the thickness of one piece is not enough, the pieces can be overlapped. Use the handle of a screwdriver or similar tool to run along the edges of the tape to ensure it is firmly attached to the metal.
Application of putty and spraying of primer and enamel
Before putting into practice the information given in this paragraph, read the paragraphs on repairing dents, deep scratches, holes due to corrosion, and holes.
There are many types of automotive fillers. But for such repairs, kits consisting of a container with a filler are better suited (resin) and a tube of hardener. To level the surface of the putty and give the correct shape to the repaired area, a wide flexible plastic or nylon spatula will be very convenient.
Prepare a small amount of putty on a clean piece of cardboard or plastic. When mixing filler with hardener, carefully measure the proportion of hardener (following the manufacturer's instructions on the packaging), because otherwise the putty will harden too quickly or never harden. Apply putty to the prepared area with a spatula. Level the surface of the putty with a spatula to achieve the desired shape. When you reach a shape close to the correct one, stop. If you continue to level the putty for too long, it will become sticky and start sticking to the trowel. Continue applying thin coats of putty at twenty minute intervals until the putty is slightly raised above the adjacent body area.
After the putty has hardened, the excess can be removed with a metal scraper or file. Then sand the surface, gradually moving from coarse to finer paper. Start with 40 grit paper and finish with 400 grit waterproof paper. Wrap the sandpaper around a flat piece of rubber, cork, or wood. Otherwise, the putty surface will not be perfectly flat. When leveling the surface of the putty with waterproof sandpaper, the paper should be periodically moistened with water. This will ensure a smooth surface in the final stage.
At this stage «dent» should be surrounded by a ring of bare metal, which in turn should be surrounded by a well-defined edge of good paintwork. Rinse the repair area with clean water until all sanding dust is removed.
Apply a thin layer of primer from an aerosol can over the entire repair area. This will reveal all the defects on the surface of the putty. Repair imperfections with fresh finishing putty (type «bodystopper») and again level the surface with sandpaper. Repeat the thinning and finishing procedure until you are satisfied with the quality of the putty surface and its mating with the undamaged paintwork. Rinse the repair area with clean water and dry thoroughly.
The repair area is now ready for final refinishing. Spray painting should be carried out in a warm, dry, windless, dust-free area. These conditions can be created artificially if you have access to a large enclosed work area. But if you are forced to work outdoors, you will need to choose your day very carefully. If you are working indoors, dampen the floor in the work area with water. This will cause dust to settle that would otherwise be present in the atmosphere. If the repair area is limited to one body panel, cover adjacent panels. This will help to minimize minor discrepancies in paint colors. Body elements (e.g. chrome trims, door handles, etc.) also needs to be closed. To close, you can use sticky tape and several layers of newspapers.
Shake the aerosol can thoroughly before spraying and test the spray on a test surface (old piece of tin or something similar). Practice the spray technique. Apply a thick layer of primer to the repair area. The required thickness is best achieved by applying several thin layers, rather than one thick one. Sand the primed surface with 400-grit sandpaper, periodically wetting it with water, until a smooth surface is obtained. When doing this, the repair area should be completely moistened with water and also periodically moistened with water in the paper. Let the surface dry before applying the next coat.
Spray on the top coat, gaining thickness again by applying several thin coats of enamel. Start applying from the center of the repair area and, using single strokes from side to side, move outward until you have covered the entire repair area and approximately 50mm of the surrounding paintwork. Remove all protective material 10-15 minutes after applying the last layer of enamel.
Allow new paintwork to cure at least two weeks. After that, using a refinisher or a very fine abrasive paste, make a smooth transition between the new enamel and the existing paintwork. And finally, apply polishing mastic.
Plastic elements
With the introduction of more and more plastic elements into the body structure (e.g. bumpers, spoilers and in some cases large body panels) the repair of serious damage to such elements now requires the involvement of a specialist in this field or is carried out by complete replacement. Self-repair of such damage is virtually impossible due to the high cost of the necessary equipment and materials. The basic technique is to cut a groove along the crack line. For this, a cutter is used, fixed in an electric drill. Then the damaged element is welded with a hot air gun, which serves to heat and melt the plastic filler rod placed in the groove. After that, remove the excess plastic and sand the repair area until it is even. It is important to use the correct plastic filler rod as body parts can be made from different types of plastic (e.g. polycarbonate, polypropylene, etc.).
Less serious damage (abrasion, minor cracks, etc.) can be repaired by yourself using a two part epoxy putty/adhesive. Once mixed in equal proportions, it is used in a manner similar to body putty used on metal panels. Putty usually hardens within 20-30 minutes and becomes suitable for grinding and painting.
If the owner replaces the entire element himself or repairs it with epoxy putty/adhesive, he will inevitably face the problem of finding an appropriate exterior paint that is compatible with the plastic used. At one time, the use of universal paint was not possible due to the complex combination of plastics that are used to make body parts. Standard paints generally do not adhere satisfactorily to plastics or rubber. However, it is now possible to purchase a kit for painting plastic body parts, which includes a preliminary primer, a base primer and a colored enamel for the outer layer. The kit usually comes with detailed instructions, but basically the technique is to first apply a pre-primer to the problem element and let it dry for 30 minutes. Then the main primer is applied and before the final application of a special colored outer layer, it is left to dry for about an hour. As a result, you get a correctly painted element, on which the paint will be elastically deformed along with plastic or rubber. Standard paint usually does not have this property.