E30 series BMW 3

since 1983-1994 of release

Repair and car operation

+ 1. Maintenance instruction
+ 2. Maintenance
+ 3. Engine
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
+ 7. Exhaust system
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
- 14. Good advice
   14.2. Changed numbers
   14.3. Purchase of the old car or mysterious set of figures and letters
   14.4. Durability of the car
   14.5. About parallelism of bridges of the car and the trailer
   14.6. Preparation of the car for winter
   14.7. Rule 35
   14.8. Choice of the second-hand car
   14.9. Engine oils
   14.10. That it is necessary to know, changing oil
   14.11. Emergence in deposit oil
   14.12 whether. It is possible to mix import oils?
   14.13. "Eats" much, but silently goes
   14.14. It is rather live, than it is dead …
   14.15. It is not got - good advice
   14.16. Visit to car-care center
   14.17. A gear belt for a drive of the mechanism of a gazoraspredeleniye
   14.18. Wear of pistons
   14.19. Valves
   14.20. Bearings of engines
   14.21. Engine pollution
   14.22. As the conditioner works and what to do, if it failed
   14.23. Conditioner: not only "pluses", but also "minuses"
   14.24. Rules of service of the conditioner
   14.25. It is not necessary to stir antifreeze with antifreeze …
   14.26. That it is necessary to know upon purchase of the air filter
   14.27. Engine overheat
   14.28. That it is necessary to know to the owner of the car with the injector engine
   14.29. Accumulator
   14.30. Possible malfunctions of the storage battery
   14.31. What to do with the failed generator
   14.32. The belt is guilty, and we blame the generator
   14.33. Catalyst
   14.34. Rub in one - or how to save the catalyst
   14.35. Probuksovochka
   14.36. Features of operation of brake system
   14.37. Malfunctions of brake system
   14.38. Brake liquids
   14.39. ABS: natural choice
   14.40. Rims
   14.41. We update rims
   14.42. Scheme of marking of a car tire
   14.43. Metal corrosion
   14.44. Automake-up
   14.45. What creaks?
   14.46. Hatch
   14.47. Safety cushion: troubles or pleasures?
   14.48. We fit well?
   14.49. Anticreeping "immunodeficiency"
   14.50. Why headlights grow dull
   14.51. "Galogenki"
   14.52. About the correct adjustment of headlights
   14.53. Electric motor
   14.54. From change of places "composed" changes nothing?


14.43. Metal corrosion


About 70 % of cost of the car are defined by a body condition. And it, in turn, depends on, whether the car visited failure and, the main thing, from extent of its corrosion damages.

The reasons causing accelerated corrosion, are subdivided into two groups and are connected:

– with design or technological features of concrete models;
– with external influences.

It is possible to carry to the first group:

– emergence of high tension and vibrations of metal of a body;
– existence of "pockets" in bearing sections of bodies;
– use of a thin metal leaf (0,7–0,8 mm);
– metal use with the impurity increasing speed of corrosion;
– existence of concentrates of corrosion in the form of moldings and other ornaments.

External influences treat:

– sulphurous connections, dioxide of carbon and the chlorides containing in environment;
– the salt solutions applied to fight against ice.

Under our conditions the greatest influence is rendered by various salt solutions as lead to formation of current-carrying "bridges" between body details, as a rule, having different electric potential. It causes the most swift-flowing type of destruction of metal – electrochemical corrosion. An essence that all cars have the single-wire electroscheme, and, therefore, on a body currents from one consumer to another "walk".

Let's not go deep further into the theory, having left it to experts in the field of corrosion, and we will address to practical questions. These results are based on use during examination of three types of the devices, allowing to estimate:

– change of thickness of "live" metal, that is not undergone to impact of corrosion;
– degree of an erosion of metal from the inside, in other words, degree of its razrykhleniye or destruction by oxides;
– thickness of cosmetic layers (paint, a shpatlevka) that allows to define, whether there was a body under repair and attempts it to hide.

Results of examinations which are carried out by experts, allow to draw the following conclusions:

1. In the conditions of our region speed of penetration of corrosion in metal for cars with winter operation makes – 0,2 mm a year and 0,1 mm a year for the cars which were not seeing salts.

2. Corrosion in the zones which were exposed to body repair, and absolutely quickly if this repair was made with welding or soldering use as electrochemical pairs from diverse metals are created especially quickly develops. For buying the car, in particular a foreign car, it is essentially important. After all not for nothing economical Europeans practically always sell even slightly beaten car (the truth, having received an insurance) for nothing – $1-2 thousand. For how many them then resell in our markets, the reader, probably, knows also itself. But if to you has the luck to find the latent defect before purchase commission, know that real cost of such car for 25–50 % is lower, than at the unbeaten. It is impossible to forget that sooner or later you will sell the car, and without experts expensive purchases are done now only by very naive people.

3. Most quickly there is a corrosion process in the cars, being maintained in the winter and being stored in garages, especially warm, without preliminary dissolution of salts by flowing water. We emphasize, not washings off, namely dissolution. Those who believe very are mistaken that, washing away a strong stream the lower part of the car, they do a good work. Salts are easily dissolved and without a strong pressure, and here sheetings from a powerful stream quickly enough "come unstuck" from metal, sag, creating only protection illusion. In being formed between metal and the sagged mastic cavities corrosion develops much quicker, than on open metal.


Extremely it is not recommended to wash the car with hot water as because of different temperature expansion sheetings getting warm first of all "slip" from metal, forming a negative effect.

Those who believes are not right that the sheeting is thicker, the better. In total just the opposite. The main thing that in a covering there were no gaps, and therefore is necessary to update it regularly.

In summary – a practical advice. From two cars what is younger" is better not, and on what process of destruction of metal did not get on depth more than 0,4-0,5 mm. In this case any processing it is impossible to prevent formation of holes in one and a half-two years. And on the contrary, even the old car possessing since the beginning of operation reliable protection, will serve as early as more many years. Under our conditions in a foreign car it is possible to repair the engine and a running gear, but it is economically inexpedient to repair strongly rotted through body.