Anti-corrosion compounds
The most susceptible to corrosion are the load-bearing hollow sections of the body, the bottom, the lower parts of the doors, pillars, as well as the joints of body parts, including the places of spot welding. Corrosion develops most quickly in hidden cavities and lower parts of the body when moisture, dirt, salts and acids get on the surfaces.
Some specific causes of corrosion and methods for eliminating it are given in Table 37. During vehicle operation, additional protection of the internal surfaces and hidden cavities of the body is required (application of special anti-corrosion compounds) and connections of parts - by applying sealing mastics.
The materials used for anti-corrosion treatment are listed in Table 38.
Auto preservative Movil is used to treat hidden cavities. It is recommended to treat cavities at least every 1-1.5 years. It is allowed to treat surfaces previously coated with nigrol or other oils, as well as rusty surfaces with Movil.
Protective lubricant NGM-ML is used for treating hidden cavities. This material is used to treat cavities of new cars.
Protective film coating NG-216B is used to cover parts of the car under the body.
Anti-noise mastic, bitumen BPM-1 is used to protect the bottom of the car body from corrosion and to reduce noise and vibration. The mastic is applied by spraying or manually with a thickness of 1.0-1.5 mm.
Plastisol D-4A is used for sealing welded seams on the outer areas of the body.
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Non-drying mastic 51-G-7 is used for sealing joints of body elements.
The anti-corrosion substance is sprayed into hidden cavities using air or airless spraying. Air spraying requires compressed air with a pressure of 5-8 kgf/cm², a spray gun with a tank, hoses and extended nozzles for the gun. The best quality of the coating is achieved with airless spraying under a pressure of 90-100 kmf/cm², which allows spraying materials of significant viscosity.
Preparation and anti-corrosion treatment of hidden cavities
Due to the use of complex technological equipment and the need for high-quality work, it is recommended that the treatment of hidden cavities be performed only at vehicle service stations.
Sequence of treatment with anti-corrosion compounds:
- 1. Place the car on a lift, remove parts and upholstery that prevent access to hidden cavities.
- 2. Wash with water at 40-50°C through technological and drainage holes hidden cavities (Table 39), the bottom of the body, wheel arches until clean water flows out. In this case, the rotary windows should be closed, the drop-down windows should be raised.
- 3. Remove any water that has entered the interior and trunk, blow out all hidden cavities and other areas where anti-corrosion compounds have been applied with compressed air.
- 4. The car is driven into the chamber for applying the anti-corrosion compound and placed on a lift. The anti-corrosion compound is sprayed onto the areas indicated in Fig. 202, 203 and 204.
- 5. Lower the car from the lift and clean the front surfaces of the body from dirt with a rag soaked in white spirit.
Restoration of complex anti-corrosion and anti-noise coating of the underbody and wheel arches
During vehicle operation, the coating on the underbody is damaged and worn away by exposure to gravel, sand, salt, and moisture. The exposed metal is subject to corrosion.
At the automobile plant, BPM-1 mastic was applied to the lower surface of the body base and side members for noise insulation and protection against corrosion.
Before restoring the coating, place the car on a lift, carefully inspect the underbody and identify coating defects. Clean the underbody from dirt, remove rust with a spatula or sandpaper. Blow the underbody with compressed air. To remove rust, you can use the Omega-1 auto rust cleaner or auto rust converters.
The car is placed on a lift in the mastic application chamber and the wheels are removed. The brake drums and discs are covered with protective covers, the cardan transmission, muffler, cables and other places that are not subject to mastic treatment are insulated with thick paper and adhesive tape.
Degrease the areas stripped to bare metal with a rag soaked in white spirit. Apply GF-073 primer to the areas stripped to bare metal with a sprayer or brush and leave for 5-10 minutes.
On defective areas by spraying or manually (with a brush and a spatula) apply BPM-1 mastic in a layer of 1-1.5 mm.
In the cold season, before use, the mastic is kept in a warm room until the temperature rises to at least 20°C. The thickened mastic is diluted with xylene to 3% by volume.
Paintwork contaminated with mastic is cleaned with a rag soaked in white spirit.
Dry the mastic at a temperature of 100-110°C for 30 minutes or at 18-20°C for at least 24 hours.