Cosmetic corrosion appears on the outer surfaces in the form of pitting rust at the points of contact of the body with overhead parts - decorative overlays, lights, as well as on the edges of the door flanges, hood, trunk lid. This type of corrosion appears primarily where the paintwork is damaged. Deteriorating the appearance of the car, cosmetic corrosion, if left untreated, progresses and turns into penetrating corrosion.
Penetrating corrosion affects the most difficult to visually control places where moisture and dirt accumulate. It is discovered when the damage it has caused is difficult to repair. The inner surfaces of box-sections, the surfaces of the front and rear fenders, the thresholds and floor crossbars, the floor itself from the passenger compartment, and the internal cavities of the doors are most susceptible to its influence.
Structural (through) corrosion affects the attachment points to the body of the power unit, chassis, elements that form the supporting frame of the body. Particularly susceptible to structural corrosion are elements that experience abrasive and corrosive effects - the bottom, sills, wheel arches, front and rear fenders. The loss of mechanical strength of these elements leads to failure of the entire car body.
Restore areas affected by corrosion immediately upon detection of its traces on the paintwork or in places where the mastic has peeled off.
The most radical rust removal method is mechanical, although it is more laborious. The combination of chemical and mechanical treatment of the affected areas is the most appropriate and effective.
Restoration of areas affected by corrosion, carry out in the following order.
For easier rust removal, moisten the damaged area with mineral spirits or auto cleaner «Omega 1». Remove corrosion products with metal brushes, scrapers of various shapes, spatulas, grinding wheels and cloth- or paper-based skins.
Clean to a metallic sheen of damage from rust, old primer and paint, bituminous or plastisol coating.
Rinse cleaned areas with water, dry and degrease.
Apply with a brush a phosphating agent of the type «phosphator».
Dry the treated surface for 25–30 minutes at 18–20°C.
On the prepared surface, apply a quick-drying primer of a phosphating or passivating type with a low drying temperature, such as VL-2 or VL-08 (phosphating primer, drying temperature 15-20°C, drying time 24 hours) either GF-073 or NTs-097 (passivating primer, drying temperature 15–20°C, drying time 4 hours).
After the first layer has dried, apply a second layer of primer. Let it dry slightly and paint with decorative enamel.
Effective control of structural corrosion is the most time-consuming and costly. It consists in inspecting the car, the necessary disassembly and replacement of individual affected body elements or the removal of damaged areas and welding overlays to these places. The installation of overlays does not solve the problem, but only somewhat slows down the development of through corrosion of the body. Replacing damaged elements from spare parts or new elements will extend the life of the body by another 10–15 years.
Restoration of the paintwork is inevitable during the operation of any car.
Elimination of minor scratches that do not affect the metal of the body, carry out in the following order.
Remove loose paint particles by sanding the damaged area with fine sanding paste.
Rinse the treated surface with clean water, degrease and dry.
Apply a thin coat of paint to the scratch with a small brush.
Continue to apply thin coats of paint layer by layer until the surface inside the scratch reaches the level of the surrounding surface of the panel.
Let the new paint cure for two weeks.
Sand the painted surface flush with the surface of the rest of the panel with a very fine sanding paste.
Treat the repaired surface with wax.
If the depth of the scratch has reached the metal surface and caused corrosion, do the following:
- remove rust with a scraper;
- treat the surface with an inhibitor compound to prevent further development of corrosion deep into the metal;
- dilute the putty slightly with a solvent and apply it with a rubber applicator (spatula) for a scratch;
- let the putty dry slightly;
- put a cotton glove on your hand, moisten your index finger with solvent and run along the scratch - a slight notch should form on its surface;
- after the putty dries, paint the damaged area.
Body putty
Puttying prior to painting allows you to restore the geometric surface of the repaired body panel. Many types of body putties are produced, but putty with a hardener behaves best in work, you just need to strictly follow the manufacturer's recommendations. Putty is applied with a flexible rubber or plastic applicator. Mix a small amount of putty on a clean wooden or cardboard surface, sparingly using the hardener.
Puttying is carried out in the following order.
Prepare the metal surface as described above.
Prepare putty according to manufacturer's instructions.
Use an applicator to apply putty to the damaged area of the body panel. To achieve the desired surface contour and putty level, each stroke of the applicator should go through the entire surface to be repaired. As soon as the contour of the putty surface approaches the contour of the undamaged surface, immediately stop applying the putty, as it will begin to stick to the applicator, forming lumps and leaving scuff marks.
Apply layers of paste at intervals of about 20 minutes until the level of the putty surface is slightly raised above the surrounding metal of the panel.
Allow the treated surface to dry completely and harden.
Remove excess putty with a waterproof sandpaper: first coarse grit type N-180, then, gradually reducing the grit, finish with N-600 sandpaper. It is recommended to use imported materials due to the higher quality of the abrasive and lining.
For best results, it is recommended to pre-wrap (or stick) paper around a wooden block (You can use rubber or foam).
Moisten the sandpaper with water regularly and abundantly during the processing. Carry out the work until the absolute smoothness of the treated surface is achieved.
At the final stage, the treated surface should appear as a disk or oval of clean surface, ending with a gradually fading edge of well-preserved paint.
Rinse the treated area with plenty of running water to remove the smallest abrasive particles formed during the grinding process.
Dry, degrease and dry the surface again with a hair dryer.
Apply a thin layer of primer from an aerosol can, thus revealing all defects made during grinding.
Eliminate the detected defects by applying a layer of fresh putty.
Repeat the sanding and sanding steps.
Repeat the steps of puttying, sanding and priming until you get a satisfactory result.
Finally, rinse the treated surface with running water and dry it - the surface is now ready for painting.
Body painting
Painting of the panel surface must be carried out in a dry, clean and pre-ventilated area. The air in the room must be dry, clean and still.
Carry out coloring in the following order.
Select the section of the panel to be painted; cover the rest of the surface with thick paper, secured with adhesive tape. Leave a 50 mm wide area of the undamaged surface open around the perimeter. thin paper (newspaper) use in multiple layers.
Before painting, check the operation of the spray gun or aerosol can on the supporting surface (cardboard) and practice the coating technique.
Prime the surface. The required thickness is achieved due to the multi-layering of thin primer layers. Dry the surface to be treated before applying each coat of primer.
Sand the surface with moisture-resistant N-600 sandpaper, not sparing running water. Achieve an absolutely smooth surface.
Let the soil dry completely.
Apply a layer of paint, again achieving its thickness through several layers (3–5). Apply layers «wet», allowing the previous layer to dry slightly.
Start painting from the center of the repaired area, moving your hand with a spray gun (spray can) in a spiral, expanding the reach until the entire damaged surface is covered, as well as a ring of the surrounding surface with a width of approximately 50 mm.
After 10-15 minutes, not later, after applying the last layer of paint, remove the paper and adhesive tape that covered the body panel.
The paint is completely dry (polymerizes) in two weeks.
Only then proceed to leveling the color transition by treating the restored surface with a very fine sanding paste.
Finally, apply a coat of AB-70 wax to the restored panel. If less than 4 years have passed after painting the body, then you can use car polish.
If after the application of this technology it was not possible to achieve satisfactory results, you can use the PMA-2 grinding paste. If this does not help, then you will have to completely repaint the body. Reuse of PMA-2 paste is not allowed.
Elimination of small body defects
The resulting deformations of the outer surfaces associated with their minor damage are eliminated in two ways - punching and straightening, after which the paintwork is restored. If the use of a drift is difficult due to the impossibility of access from the reverse side, the damage is eliminated by external stretching and the use of polymeric materials.
Eliminate minor damage in the following order.
Remove the old paintwork from the damaged area and prepare the surface as described above for painting.
Cover the surface cleaned to the metal with a grid of scratches, which will ensure maximum adhesion of the putty and the surface to be treated.
Depending on the maximum depth of damage, prepare:
- polyester putty brand PE-0089, if the damage depth does not exceed 2.5 mm. Before use, mix the mass with a hardener (100:2,0) and apply with a spatula on a surface cleaned to a metallic sheen and degreased;
- epoxy adhesive based on resin type ED-20, if the damage depth does not exceed 4 mm;
- EP-0020 brand epoxy putty, if the damage depth does not exceed 7 mm. Before use, mix the mass with a hardener (100:8,5) and apply with a spatula to a metallically polished and degreased surface.
- Apply several thin layers of putty until the surface is close to the original shape, with a slight protrusion above it.
Let the putty harden to the point where it is pressed through with a fingernail.
Proceed with surface preparation for refinishing as described above.
The highest quality of repair work is achieved when using polyester fillers.