The hollow sections of the body, the bottom, the lower parts of the doors and pillars, as well as the joints of body parts, including spot welding, are most susceptible to corrosion.
Corrosion develops most quickly in hidden cavities and lower parts of the body when exposed to moisture, dirt, salts, and acids. In this regard, during the operation of the car, a special anti-corrosion compound is applied to additionally protect the internal surfaces and hidden cavities of the body, and sealing mastics are applied to the joints of the parts.
The anti-corrosion compound used to treat the internal cavities of the body and the bottom must meet the following requirements:
- contain corrosion inhibitors;
- evenly distributed over the entire treated surface and create a protective film that is resistant to vibration and temperature changes;
- have good adhesion to body elements or previously applied coatings;
- be compatible with previously applied paint coatings and anti-corrosion compounds;
- retain their physical and chemical properties for a long time under the influence of external factors;
- contain materials that, when used to treat a vehicle, meet fire and environmental safety standards.
Auto preservative "Movil" or "Movil-2" is used to treat hidden cavities. It is recommended to treat cavities every 1-1.5 years. Auto preservative allows the treatment of surfaces previously coated with nigrol or other oils, as well as rusty surfaces.
Protective lubricant NGM-ML is used for processing hidden cavities. This material is used to process hidden cavities of new cars.
Protective film coating NG-216B is used to cover parts of the car under the body.
Bitumen anti-noise mastic BPM-1 is used to protect the underbody from corrosion and to reduce noise. Coating thickness 1.0–1.5 mm.
Plastisol D-11A is recommended for protecting the underbody from corrosion, abrasive wear and for noise insulation. Coating thickness 1.0–1.2 mm.
Plastisol D-4A is intended for sealing welded seams.
Non-drying mastic 51-G-7 is used for sealing body joints.
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The anti-corrosion substance is sprayed into the internal cavities using air and airless spraying.
Air spraying requires compressed air at a pressure of 0.5–0.8 MPa, a spray gun with a tank, hoses and extension nozzles for the gun. The best coating quality is achieved with airless spraying at a pressure of 4–12 MPa, which allows spraying materials of significant viscosity.
For mechanical protection of wheel arches from small stones and sand, in addition to the standard arch protection installed at the manufacturer, plastic mudguards are used, additionally installed on the car. The main disadvantages of additional mudguards are drilling additional holes in the wing for their fastening, deterioration of ventilation of wheel arches, accumulation of dirt and salt in places where the mudguard protrudes above the wing flange. To protect the paintwork of the front part of the hood and the lower part of the doors, special anti-gravel transparent self-adhesive films are used.