Rust… the number one enemy of almost any metal. “Red plague”, with an enviable tenacity and persistence, transforming hundreds of thousands of tons of sparkling high grade, high strength, alloy steel in the piles of brown powder. Disease for which there are no barriers… But there are medicines and from her: electroplating, Lani and paint, bitumen and mastic — all they basically have to protect the metal. But the reality is not so simple.
Very acute problem of protection against corrosion is, for example, in front of motorists. It is well known that if you do not take certain measures, the body of the car in the next four to five years can become literally a rusty sieve. Often do not have any help of paint, no mastic, because the body has a lot of closed cavities, sinuses, pockets, boxes in which road dirt and dampness, mixed with the salt, creating perfect conditions for electrochemical corrosion. And at present the thickness of automotive steel sheet, it leads to a very quick breakdown.
But corrosion is possible not only to protect the armor from lacquer or chrome, you can cheat, given in the form of a bait a piece of cake, as the metal with the higher electrode potential.
Electrode potential? And what he actually is related to the corrosion of metals? It turns out that the most direct.
If you put it in a container of electrolyte, two electrically connected metal electrode, then one of them begins to dissolve, the other will remain in neprikosnovennosti. So, it appears, dissolves the metal, electrode potential which is higher. This property of a galvanic couple and given the opportunity to use the preservation effect of the cathode for protection against electrochemical corrosion of the car body.
Fig. 1. Kit for anodic protection of a car body:
1 — serebranny the zinc electrode, 2 — wire connection.
Boat builders have long used this principle of protection of the inner part of the hold against corrosion — they are placed inside the case special metal anodes (made of metal with a higher electrode potential than the metal of the case). This method has recently been adopted by motorists.
For the anode used finned (to increase the surface area) pieces of zinc. With them embedded in permanent magnets they are attached in the most remote and polluted places on the body. Electrical connection is stranded wire: with screws zinc anode and is connected to the body.
On his ribs is going to road dirt, moisture, salt, and a set of “zinc steel” begins to work as it works with all known galvanic cell. When such “battery” is the dissolution of the zinc anode, the cathode in this case is not consumed.
The corrosion process resembles the work of a galvanic cell, as the steel is basically an alloy of iron and carbon, that is, materials with different electrode potentials. The NC in contact with the surface of the alloy electrolyte between the grains of iron and carbon begins to walk electrochemical reaction accompanied by dissolution of the anode (iron) and transfer it into hydrates and then into oxides.
Fig. 2. The installation of the electrodes at these points of the most effective:
1 — box amplifiers mudguards, 2 – the attachment of the housings of the headlights and sidelights, 3 — lower part of front panel, 4 — cavity for shields amplifier front fenders, 5 — inner surface of the doors 6, 7 — the front lower part of the rear wing and wheel arch at the junction of the wing, 8 — apron rear panel.
Fig. 3. The installation of the electrode in the wheel well.
The presence of the same electrically connected to the metal zinc of the electrode dramatically changes the picture. With respect to both the iron and carbon zinc is a metal with a higher electrode potential, that is, acts as the anode. Therefore, in the presence of a conductive medium, which is almost always present on the surfaces of the automobile body, an electrochemical reaction takes place with dissolution of the anode (zinc), while maintaining the cathode, i.e., metal kusasa.
As shown by the experiments, zinc electrode the size of a matchbox is enough for 3-5 years.
Deceive “red plague”. Slip her the bait — a piece of metal with spectrogram potential higher than that of steel. Corrosion willingly clung to him, forgetting about the body is your vehicle for at least three years.
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