During the operation of the car, it is necessary to check the condition of the anti-corrosion coating and, if necessary, additional protection, especially hidden cavities, by applying special anti-corrosion compounds, and connecting parts - by applying sealing mastics. For the introduction of anti-corrosion compounds into the hidden cavities behind the manufacturer's water, technological holes and openings are provided through which the tips of the guns can be passed. After the introduction of the composition, the holes are closed with rubber plugs. Particular attention during the operation of the car should be paid to the integrity of the protective coating on the bottom of the body, which is subject to more intense external influences, and hence corrosion.
The materials used for anti-corrosion treatment are listed in Table. 31.
Protective lubricant NGM-ML is used for processing hidden cavities. The hidden cavities of new cars are processed with this material.
Auto Preservatives «Movil» and «Movil-2» are used for processing hidden cavities during operation. It is allowed to apply autopreservative on surfaces previously covered with oils, as well as on a rusty surface. It is recommended to treat cavities every 2 years.
The protective film coating NG-216B is used to cover the components and parts of the car under the body for the period of transportation. Plastizol D-11A is used to protect the bottom of the body from corrosion, abrasive wear and for soundproofing new cars. Coating thickness 1-1.5 mm.
Anti-noise bituminous mastic BPM-1 is used to protect the underbody from corrosion during vehicle operation. Mastic is applied with a thickness of 1-1.5 mm. It reduces noise well, but has insufficient anti-corrosion properties and cannot withstand salt solutions, abrasives and other substances for a long time. Plastisol D-4A is used for sealing welds and joints of parts on the outer and inner surfaces of the body.
Non-drying mastic 51-G-7 is used for sealing body joints, corner joints and gaps.
Anti-corrosion compounds must be applied evenly and without pores. For application in the hidden cavities of the body, a KRU-1 gun with a special elastic tubular plastic extension is used. The extension cord is connected to the air gun with a union nut at one end, and has a spray nozzle at the other end, which creates a spray jet. Due to its elasticity, the extension ensures the penetration of the spray nozzle into hard-to-reach places in the body.
The anti-corrosion composition is applied to the surface by air and airless spraying. Air spraying requires compressed air at a pressure of 0.3-0.4 MPa, which is fed into the spray gun with a tank and then into the sawing nozzle. The best quality of the coating is achieved with airless spraying under pressure on the anti-corrosion compound up to 16 MPa, which allows sawing materials of significant viscosity.
Preparation and anti-corrosion treatment of hidden cavities
Due to the need for sophisticated technological equipment to perform work and the requirement for high-quality work, it is recommended that processing be carried out at car service stations. The procedure for performing operations for corrosion protection of hidden cavities is as follows:
- install the car on a lift, remove parts and upholstery that prevent access to hidden cavities;
- washed with water at a temperature of 40-50°C through technological and drainage holes hidden cavities (tab. 32), bottom of the body and rear wheel arches. It is necessary to flush hidden cavities until clean water flows out of the holes. In this case, the sliding windows of the doors must be raised;
- remove water that has entered the cabin, blow out all hidden cavities and places where anti-corrosion compounds are applied with compressed air;
- they drive the car into the chamber for applying the anti-corrosion compound and put it on a lift. Apply by spraying the anti-corrosion composition to the places indicated in fig. 188;
- lower the car from the lift, clean the front surfaces of the body from dirt with a rag soaked in white spirit.
Restoration of anti-corrosion anti-noise coating of the underbody and wheel arches
During the operation of the car, the coating on the bottom of the body is exposed to gravel, sand, salt, moisture, as a result of which the mastic and soil are damaged and erased. Bare metal corrodes.
At the car factory, on the lower surface of the body base, wheel arches and spars for sound insulation and protection against corrosion and abrasive wear, either BPM-1 bituminous mastic 1–1.5 mm thick or D-11A plastisol 1–1.2 mm thick is applied over epoxy primer EF-083.
In case of damage to the D-11A plastisol coating without disturbing the soil layer, the damaged areas are cleaned of dirt, degreased, and plastisol is applied to a dry surface by airless spray or brush. Dry the plastisol at 130°C for 30 minutes. Due to the significant complexity of heating the body coating to a high temperature and the need for complete disassembly of the vehicle, it is allowed to restore the coating by applying bituminous mastic BPM-1, which can be dried in natural conditions.
Before restoring the coating, install the car on a lift, carefully inspect the bottom of the body and identify defects in the coating. They clean the bottom of the body from dirt, remove rust with a spatula, sandpaper or rust converter according to the instructions for its use. Blow the bottom of the body with compressed air. Then put the car on a lift in the mastic chamber and remove the wheels. They close the drums and brake discs with protective covers, insulate the driveline, mufflers, cables and other places that cannot be treated with mastic with thick paper and adhesive tape. With a rag soaked in white spirit, the places cleaned to the metal are degreased, primer GF-073 is applied to them by spraying or brushing and allowed to dry for 5-10 minutes. Then applied by spray or by hand (brush or spatula) mastic BPM-1 on defective places with a layer 1-1.5 mm thick. The application of mastic to adjacent areas that do not have damage should be minimal. In the cold season, the mastic is kept in a warm room before use until the temperature rises below 20°C. In case of mastic thickening, it is diluted with xylene, adding no more than 3%.
When contaminated with mastic, the paintwork on the front panels is cleaned with a rag soaked in white spirit. The mastic is dried at a temperature of 18–20°C for at least 24 hours. To speed up drying, the coating is kept at 100–110°C for 30 minutes.
Body sealing
Rubber seals are used to ensure tightness (pic. 189) various profiles, sealing mastics, rubber plugs for technological holes, and also carefully adjust all mating parts. Seals 4 of the front door opening are made of sponge rubber in the form of a tube, to which a plastic facing edge with a perforated metal frame is welded. The frame provides fastening of the seal on the flange of the door opening. The inner part of the seal is connected to the atmosphere through holes in the sponge rubber.
Pic. 189. Rubber body seals: 1 - windshield seal: 2 - air intake box seal; 3 - seals for the grooves of the sliding windows; 4 - front door opening seals; 5 — a sealant of an aperture of a door of a back; 6 - tailgate glass seal; 7 - sidewall glass seal; 8 - lower seals of the sliding window: 9 - seal of the sliding window holder; 10 - front door opening seal frame.
The openings of the wind window, rear windows and sidewalls are sealed with rubber seals 1, 6, 7, which have special tongues to ensure a tight fit. The air intake box, as well as the tailgate opening, are sealed with rubber seals 2 and 5, respectively, which are held on the body flanges by metal perforated frames of the seals.
Seals for 3 guide grooves for lowering glass doors are made of rubber of a special profile, on the sealing surface of which pile is glued to reduce glass friction. The lower glass seals 8 are also covered with pile to eliminate twisting and creaking of the seal when lowering and raising the glass.
When removing and installing seals with a metal frame, collapse of the frame and the formation of corrugations on the seals are not allowed.
Welded seams of body elements from moisture, dirt and corrosion protection are sealed with D-4A plastisol after priming the body. Welded seams after replacing body parts during repair are coated with plastisol on both sides. Plastisol hardens during drying of the body after painting work.
Sealing gaps and joints in the joints of body parts (pic. 190) carry out non-drying mastic 51-G-7.
Pic. 190. Joints and gaps on which non-drying mastic 51-G-7 is applied: 1 - joints of the middle cross member with the arches of the rear wheels; 2 - corner joints of mudguards and racks of the wind window frame; 3 - corner joints of the connectors of the threshold of the floor and mudguard; 4 - joints of the right and left partitions with the frame of the wind window; 5 - corner joints of protective covers and rear floor; 6 - corner joints of the bulkhead extension with the right and left partitions; 7 - corner joints of the bulkhead and mudguard.