11.24.4. Anticorrosive protection of a body
At daily operation of the car the paint and varnish and anticorrosive covering of a body is influenced by hostile environment: deicing reagents (during the winter period of time), sand, small stones, vibration and temperature drops which cause emergence of microcracks in a body sheeting through which water and oxygen get to the surface of metal. As a result of impact on a body of hostile environment metal oxidation process begins (corrosion) which leads to loss of strength properties by it, and existence in water of a large amount of salts and acids only accelerates oxidation process.
Hollow profiles of a body, the bottom, the lower parts of doors and racks, and also connections of details of a body, including the place of spot welding are most of all subject to corrosion.
Most quickly corrosion develops in the hidden cavities and the lower parts of a body at hit of moisture, dirt, salts, acids. In this regard in use the car for additional protection of internal surfaces and the hidden cavities of a body put special anticorrosive structure, and in connections of details — sealing mastics.
The anticorrosive structure which process internal cavities of a body and the bottom has to meet the following requirements:
– to contain corrosion inhibitors;
– to be distributed evenly on all processed surface and to create the protective film resistant to vibration and temperature drop;
– to have good adhesion with elements of a body or earlier put coverings;
– to be compatible to the put earlier paint and varnish coverings and anticorrosive structures;
– to keep the physical and chemical properties long time under the influence of external factors;
– to contain materials which when processing the car answer standards of fire and ecological safety.
Movil or Movil-2 autopreservative is used for processing of the hidden cavities. It is recommended to process cavities every 1-1,5 year. Autopreservative allows processing of the surfaces which are earlier covered nigroly or other oils, and also rusty surfaces.
The NGM-ML protective lubricant is applied to processing of the hidden cavities. This material processed the hidden cavities of new cars.
The protective film covering of NG-216B is used for a covering of parts of the car under a body.
Mastic antinoise bituminous BPM-1 is applied to protection of the bottom of a body against corrosion and to noise reduction. Thickness of a covering is 1,0–1,5 mm.
The plastisol of D-11A is recommended for protection of the bottom of a body against corrosion, abrasive wear and for a noise isolation. Thickness of a covering is 1,0–1,2 mm.
The plastisol of D-4A is intended for sealing of welded seams.
Non-drying mastic 51-G-7 is used for sealing of joints of a body.
In internal cavities anti-corrosive agent is napylyat in the way of air and airless dispersion.
At air dispersion compressed air under pressure of 0,5–0,8 MPas, the gun spray with a tank, hoses and lengthening nozzles for the gun is required. The best quality of a covering is reached at airless dispersion under pressure of 4–12 MPas which allows to spray materials of considerable viscosity.
For mechanical protection of arches of wheels against small stones and sand, besides the regular protection of arches established at manufacturer use the flaps from plastic which are in addition installed on the car. The main shortcomings of additional flaps — drilling in a wing of additional openings for their fastening, deterioration in ventilation of wheel arches, a congestion of dirt and salt in places of a vystupaniye of the flap over a wing otbortovka. Apply special anti-gravel transparent self-adhesive films to protection of a paint and varnish covering of a forward part of a cowl and the lower part of doors.