Corrosion is translated from Latin as "corrosion". This is the name of the process of destruction of any material (wood, ceramics, polymer, metal) as a result of exposure to the environment, whether it be soil, air, water (sea, river, marsh, lake, underground) or any other medium. As applied to metals, the term metal corrosion is replaced by the generic word “rust”. For example, during oxygen corrosion of iron in water, hydrated iron hydroxide is formed - ordinary rust.
Corrosion of metals leads to large losses - for Russia this is the annual loss of millions of tons of valuable metals. More than 10% of the annual production of
metal pipes becomes unusable due to corrosion. For the same reason, the metal structures of various structures buried in the ground, storage tanks for oil and other
minerals become unusable in 3-4 years, if they are not protected from the destructive effect of soil and ground corrosion. Electrical and communication cables, bottoms of swimming aids, car bodies and other vehicles are corroded.
Soil corrosion of metals is an electrochemical process that depends on such factors as the chemical composition of soils, their moisture and air permeability, the type of metal, its uniformity, and the nature of the surface of metal objects.
In order to protect metal in the ground (water, air, other environments), you need to know the reasons that can cause corrosion of metals. To obtain data on the degree of corrosion activity of soils necessary for the development of measures to protect metal structures from corrosion, comprehensive field and laboratory studies of soils are carried out.
Protection of metals from corrosion is based on such methods:
1. increase in chemical resistance for structural materials (the introduction of corrosion-resistant elements into alloys or, conversely, the elimination of impurities that accelerate corrosion from the alloy);
2. isolating the metal surface from the effects of an aggressive environment (applying paints to metal, insulating films, galvanic coatings) ;
3. electrochemical protection - under the influence of an external current applied to a metal structure;
4. reducing the aggressiveness of the environment by introducing corrosion inhibitors (arsenates, chromates, nitrites), deoxygenation or neutralization of the medium.
These methods are divided into 2 groups. The first two methods are performed before the operation of the metal product at the stage of its design or manufacture, and it will be impossible to change anything during operation. Two other methods are carried out only during the operation of metal products and you can change the protection mode depending on the changed actual environmental conditions.
Such a question as the protection of metal from corrosion remains relevant at the present time, requiring an integrated approach to the search for modern design solutions, and the improvement of old proven protective methods and tools.