Electrochemical corrosion is the mostA common type of violation of the integrity of the metal structure. It is not necessary to immerse the part in the electrolyte. It is often sufficient to have a thin film on the surface of the material.
Electrochemical corrosion of metals occurs inmore as a result of the widespread use of technical and household salt (potassium chloride and sodium). Most often these substances are used in winter to quickly eliminate ice and snow from city streets. Most, as practice shows, damage is thus applied to underground communications and ground transportation.
Electrochemical corrosion is observed on the detailsmachines, structures, instruments in soil, soil, water (sea or river), atmosphere, in technical solutions, under the influence of lubricating, cooling products.
Destruction can provoke stray currents,which occur when a part of the current flows from the electrical circuit to the soil or water, and from there to the structural elements. Where there is a reverse exit (from metals to soil or water) there is a destruction of parts - electrochemical corrosion. Most often, wandering currents are formed in places where ground transport moves (trams, railway locomotives on electric traction). In this case, as studies show, 1 ampere per year can dissolve 33.4 kg of lead, 10.7 kg of zinc and 9.1 kg of iron.
Often in the development of destruction involves several factors.
Electrochemical corrosion is aspecial process. The alloy (or an independent material) loses some of the available atoms. They (the atoms) pass in the form of ions into the electrolytic solution. Instead of the particles lost by the metal, electrons appear that charge the material with a negative charge. In this case, the electrolyte has a positive charge. Thus, electrochemical corrosion forms a galvanic couple. The heterogeneity in the chemical structure of the material contributes to the oxidative-reduction reactions. The provoking factors in the formation of anodes and cathodes are the areas of permanent deformation, the lack of uniformity in the protective films covering the metal.
It is possible to observe the destruction of details inhome conditions. This will require three nails, three cups with salt solution (food salt dissolved in water), a small piece of zinc, copper wire (the insulation should be eliminated).
The first nail falls into a glass with saltmixture. The second should be screwed on the wire and also placed in the solution (in the second glass). The third nail is lowered into the third container. Leave for two or three days. After this period, all three nails will be rusted. However, in the worst condition there will be a nail with a wire, in the best - with zinc. This difference is due to the different ability of metals to give electrons.
To protect the material, a method of changing its potential is used. It should be noted that the technique is not related to insulation. As a protection, a cathodic (anodic) method is used.
In this case, the protected structure in(for example, in a soil medium) is attached to a cathode (a negatively charged electrode) of an electrical source. Thus, the part becomes a cathode. In the same environment, the old part is also placed, attaching it to the anode from an external source. Corrosive process leads to the destruction of the old metal, which becomes an anode.
Существует также и протекторный тип защиты.Unlike described above, this option involves the use of a special anode - the protector. In its quality, a metal more active than that of the protected structure is used. In the process of corrosive destruction, the protector performs the task of the anode (positive electrode) and, failing, protects against integrity violation in the protected part.
