Corrosion and protection of metals

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Corrosion and protection of metals

The essence of corrosion processes.

Corrosion protection methods

Passivation of metals.

Metal corrosion inhibitors

The word corrosion comes from the Latin corrodere, which means to corrode. Although corrosion is most commonly associated with metals, stones, plastics and other plastics and wood are also affected. For example, at the present time we are witnessing a great concern of wide layers of people in connection with the fact that monuments (buildings and sculptures) made of limestone or marble are catastrophically suffering from acid rain.

Thus, corrosion is a spontaneous process of destruction of materials and products from them under the chemical influence of the environment. Processes of physical destruction are not classified as corrosion, although they often cause no less damage to cultural monuments. They are called abrasion, wear and tear, erosion.

Metals are one of the foundations of civilization on planet Earth. Among them, iron stands out as a structural material. The volume of industrial production of iron is about 20 times greater than the volume of production of all other metals combined. The widespread introduction of iron in industrial construction and transport occurred at the turn of the 18th-19th centuries. At this time, the first cast-iron bridge appeared, the first ship was launched, the hull of which was made of steel, the first railways were created. However, the beginning of the practical use of iron by humans dates back to the 9th century. BC e. It was during this period that humanity passed from the Bronze Age to the Iron Age. Nevertheless, history indicates that iron products were known in the Hittite kingdom (the state of Asia Minor), and its heyday is attributed to the XIV-XIII centuries. BC e.

In nature, although very rarely, native iron is found. Its origin is considered meteorite, that is, cosmic, not terrestrial. Therefore, the first iron products (they were made from nuggets) were valued very highly - much higher than those of silver and even gold.

Despite the widespread introduction of polymeric materials, glass, ceramics into our modern life, iron and its alloys continue to be the main structural material. We meet iron products at every step in everyday life and we know how much trouble its rusting and rust itself cause. Only the corrosion of iron and its alloys is called rusting. Other metals corrode but do not rust. Although almost all metals corrode, in everyday life a person most often encounters iron corrosion.

Rigorous calculations show that most metals are prone to corrosion. Therefore, it is surprising not that metals corrode, but that products made from them can exist for a long time. The rate at which corrosion occurs is not amenable to theoretical calculations. As a rule, it is determined empirically. The speed primarily depends on the nature of the corrosion products formed and the strength of their adhesion to the metal.