Table of contents: Restoration of lightly scratched…↓ Dent repair ↓ Repair of rusted holes and punctures ↓ Puttying and painting ↓ Restoration of plastic components ↓
Restoration of lightly scratched paintwork
If the scratch is superficial and does not affect the metal of the body panel, restoration of the paintwork is extremely simple. To remove particles of peeling paint and wax coating, lightly rub the defective area with a fine grinding paste. Rinse the treated surface with clean water.
Using a small brush, fill the scratch with the same type and color of paint used to paint the panel. Continue applying coats of paint until the bottom of the scratch is flush with the surrounding body panel paint. Allow the paint to cure for at least two weeks, then sand the transition area thoroughly with a fine sanding compound. Finally, wax the repaired panel.
If the scratch has penetrated the paint and reached the metal panel, causing corrosion, the repair must be done using a different technique. Use a pocket knife to scrape off the powdery rust from the bottom of the scratch, then treat the damaged area with a corrosion inhibitor to prevent future corrosion. Using a hard rubber or nylon applicator, fill the damaged area with a gloss-type filler. If necessary, which is especially useful when eliminating narrow, deep grooves, the filler can be diluted with a special solvent. Before the filler hardens inside the scratch, wrap the tip of your finger in a soft cotton cloth, moisten it with solvent, and quickly run it along the scratch. As a result, the surface should become slightly concave. Now, after the filler has hardened, the treated area can be painted using the technique described in the first part of this subsection.
Dent repair
When repairing deep dents, the primary task is to pull out the deformed surface of the body panel in order to restore its original shape. Note that there is no point in achieving 100% compliance with the original, especially since this is unachievable due to irreversible damage to the internal structure of the metal at the moment of impact. It will be quite sufficient to bring the deformed surface to a level located 3 mm below the surface of the surrounding undamaged part of the panel. Note: If the dent is not deep, pulling it out is completely pointless.
If the deformed area can be accessed from the back of the panel, you should try to straighten the panel from the inside by tapping the metal with a soft-faced hammer. At the same time, a wooden block should be pressed tightly against the front side of the damaged area to dampen the impact impulse and avoid excessive bending of the metal being restored.
If the dent is located on a two-layer section of the body panel, or access to the latter from its reverse side is impossible for some other reason, you should change the method. Drill several small holes in the most heavily deformed areas of the dent, then screw long screws into them, leaving the heads of the latter sticking out above the surface of the metal. Now start pulling out the metal, grasping the screw heads with self-locking pliers.
The next stage of processing involves completely cleaning the damaged area and the surrounding panel surface to a width of approximately 3 cm from paint. This work is best done using a wire or grinding attachment to an electric drill. Paint removal can be done no less effectively by hand using sandpaper. The final stage of preparing the surface for puttying is roughening the exposed metal of the dent by scratching it with a screwdriver or a broken file, or drilling small holes. The roughness of the surface increases the efficiency of adhesion of the putty paste to it. Then you can begin puttying and painting the treated area.
Repair of rusted holes and punctures
Using a grinding or wire attachment on an electric drill, remove all paint from the damaged area and an area about 3 cm wide around it. The work can be done just as effectively by hand with sandpaper. After cleaning the surface from paint, you can assess the extent of metal damage by corrosion and decide whether it is advisable to repair the panel (perhaps it would be wiser to replace it entirely, if that is possible in principle). New body panels can often be purchased for not as much money as it seems - it is enough to spend a couple of days driving around city dismantlers and car dumps.
Remove all body trim elements from the damaged panel, except those that can serve as a guide when restoring the original shape of the damaged area (for example, headlight trim, etc.). Use metal shears or a hacksaw blade to remove any loose, loosely attached, or permanently corroded pieces of metal. With a hammer, bend the edges of the hole inwards to form a recess to accommodate the putty material.
Use a wire brush to remove any powdery rust from the damaged area. If the back of the panel is accessible, treat the area around the damaged area with a rust inhibitor.
Before you start filling, you should plug the hole. This is usually done by gluing or screwing a piece of tin, fine-mesh wire mesh, or aluminum foil to the back of the panel in the damaged area. Once the hole is securely blocked, you can begin filling the panel and then painting it.
The optimal material for plugging large holes is fiberglass or fine-mesh plastic mesh. Cut a piece of material to the appropriate size, insert it into the hole and secure it with an overlap on the back side of the panel using lumps of putty paste.
Aluminum foil, which comes in the form of adhesive tape, is best suited for sealing narrow holes. Simply remove the protective film and glue the foil to the back of the body panel, reliably sealing the hole. For reinforcement, the foil can be glued in several layers.
Puttying and painting
Currently, the chemical industry offers buyers a wide range of different body fillers. However, for this type of work, the best choice is the two-component filler paste with a hardener in a tube, which is offered in a set for repairing body panels. To achieve smoothness and correct shape of the filled surface, the paste should be applied with a flexible rubber or nylon applicator.
Strictly following the manufacturers instructions (violation of these may lead to incomplete hardening of the putty mass), mix a little putty on a clean wooden board or sheet of cardboard. Try to use the hardener carefully.
Apply the prepared mixture to the treated (see above) surface of the damaged area of the body panel using the applicator. To obtain the correct contour of the surface being removed, each stroke of the applicator should pass through the entire length of the area being restored. As soon as the shape of the area being restored approaches the original, immediately stop applying the filler, as it will begin to stick to the applicator when hardening, forming lumps and leaving grooves on the surface being treated. Continue applying the filler layer by layer at intervals of about 20 minutes until the surface level of the area being restored is slightly raised above the surrounding metal of the undamaged part of the panel.
After the paste has hardened, excess putty can be removed with a scraper or file. Then begins the sanding and grinding stage. This work is best done with waterproof sandpaper with uniform grain size and strong adhesion of the abrasive (preferably imported). Sanding should begin with coarse-grained paper No.40, gradually decreasing the grain size to No.400. In order to achieve adequate flatness of the sanded surface, the paper should be wrapped around a block of dense rubber, wood or foam plastic (for convenience, the paper can be glued to a block). During the surface treatment process, the paper should be regularly and frequently wetted with water. The described technology allows achieving absolute smoothness of the restored surface at the final stage of grinding.
When sanding is complete, the treated area should be surrounded by a ring of clean, exposed metal, ending in a gradually tapering edge of undamaged paint. Rinse the treated area of the panel with clean water, washing away all the abrasive formed during sanding, then dry the surface thoroughly.
Spray the treated surface with an aerosol can, covering it with a thin layer of light primer, which will help to reveal all the mistakes made during the sanding process. The detected defects are then eliminated by re-filling. Repeat the sanding stage. Continue to act in the same way until you achieve the desired shape and smoothness of the restored section of the panel. Finally, do not forget to rinse the panel with clean water and dry it.
Now you can start painting. Work with a spray gun should be done in still air in a dry, warm and dust-free room. If circumstances force you to paint outdoors, you should take the selection of suitable weather conditions very seriously. When working indoors, knock down dust by spraying the floor with water. If you are painting only a separate section of the body, cover the surrounding undamaged panels with old newspapers, securing them with adhesive paper tape. Such trim elements as chrome decorative strips, door handles, headlight trim, etc., are best removed from the body panel at the painting stage.
When using paints supplied in aerosol form, shake the can thoroughly, then spray a test surface, practicing the painting technique. Cover the surface prepared for painting with a thick layer of primer. The coating thickness should be achieved by repeatedly applying paint in thin layers. Do not spare water, sand the prepared surface with fine-grained sandpaper No.400. Allow the primer to dry completely before applying decorative paint.
Start applying decorative paint in thin layers to the primed surface. Start painting from the center of the area to be restored, making circular movements with your hand with an aerosol can/spray gun, expanding their radius in a spiral and not stopping until the entire prepared area is covered with a layer of fresh paint with an overlap of three to five centimeters. After 10÷15 minutes (better not later, so as not to damage the edge of the paint that is starting to dry) after applying the final coat, peel off the tape covering the surrounding body panels and remove the newspapers.
The final polymerization of the paint occurs after about two weeks, after which, to smooth the transition from fresh paint to old, rub the restored surface with a fine polishing paste. Finally, treat the panel with wax.
Restoration of plastic components
Repair of cracked plastic components should be entrusted to specialists. The technology is based on the use of a drill to grind a groove along the crack, into which a plastic rod of the same type of plastic as the repaired part itself is then placed. Then the halves of the cracked panel are soldered together using a special hair dryer. Excess plastic is removed by grinding.
Less serious damage can be repaired by the amateur mechanic himself by filling the defect with a 2-part epoxy compound (the technology is similar to that used for filling damaged areas of metal body panels).
When replacing a damaged plastic component, care should be taken to select a replacement panel that matches the color. Special paints and primers should be used to touch up plastic parts - ask at car accessory stores and strictly follow the manufacturers' instructions.