Over time, metal products gradually become rusty. Designs collapse, practically turn into dust. To avoid such sad results, you need to know what metal corrosion and methods of protection against it are. Metal undergoes destruction due to exposure to the external environment, which can be electrochemical or chemical. Chemical corrosion appears in environments that are not able to conduct electric current (oil products, gases, alcohols). All metals are subject to it. Electrochemical corrosion occurs due to the appearance of an electrolytic film on the metal due to environmental influences. In particular, technical and household salts used on roads in winter and stray currents have an impact . There are many ways and methods by which corrosion protection is performed.
The most popular and common is the use of coatings. They are metallic and inorganic non-metallic. Greater efficiency is provided by coatings based on the creation of synthetic polymers. Inorganic non-metallic coatings are very diverse. These include paints (oil, alkyd and enamels), as well as varnishes (tar, synthetic, bituminous). When applied, such corrosion protection creates a thin film that protects the metal from moisture and environmental influences. Varnishes and paints are very easy to apply, affordable. At the beginning of the work, it is necessary to strictly follow the technology of their application. They must cover the metal surface in several layers in order to better protect the structures from atmospheric influences.
Inhibitor metal coatings are of two types. The first includes tread coatings with cadmium, zinc, aluminum. The second - corrosion-resistant coatings of copper, silver, lead, nickel and chromium.
Depending on which mechanism the action has corrosion protection, it is called cathode or anode. There are metal coatings-inhibitors with greater electronegativity, and coatings with greater electropositivity. Anode coatings belong to the first type, cathode coatings belong to the second. Aluminum and zinc are used as anode coatings; nickel, copper, and tin are used as cathode coatings.
Various methods of protecting metals from corrosion suggest several coating options . For example, for applying inhibitors, a chemical method is used to coat metal structures with other metals: aluminum, zinc.
If the metal structure is already subjected to corrosion, then additives in the form of passivators and inhibitors will help to slow down the destruction process. Strong oxidizing agents such as alkaline earth and alkali metal salts contribute to the inhibition of corrosive processes in alkaline and neutral environments . To protect the reinforcement in reinforced concrete, calcium nitrite-nitrate is used.
When corrosion protection is needed, arising under the influence of the external environment and atmospheric precipitation, volatile inhibitors are used, which are substances that are adsorbed on the metal surface from air or condense on it, forming a thin layer.