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In fact, corrosion prevention is to extend the service life of components by adopting various means. Anti-corrosion coating is generally through shielding, corrosion inhibition, cathodic protection three methods, so that the metal even in the harsh corrosion environment, but also can maintain its performance. Heavy anticorrosive coatings in chemical atmosphere and Marine environment, generally can be used for more than 10 or 15 years, even in acid, alkali, salt and solvent medium, and under certain temperature conditions, can also be used for more than 5 years, some inorganic anticorrosive coatings used in seawater can reach more than 20 years. Strong adhesion and thick film are important marks of heavy anticorrosive coatings. Good adhesion film durable, with the required performance; Paint film with poor adhesion is easy to crack, fall off, can not be used. The dry film thickness of general anticorrosive coatings is about 100μm or 150μm, and the dry film thickness of heavy anticorrosive coatings is more than 200μm or 300μm. Anticorrosive coating is through the following three forms to achieve long-term anticorrosive purpose:

1. Shielding anti-corrosion

The shielding effect of anticorrosive coating film is to prevent the direct contact between the protected matrix and the corrosive medium, that is, the anticorrosive coating will be protected from the corrosive material and the outside world, which can effectively shield the corrosive medium, air, acid rain, etc., protect the substrate from corrosion and rust, so as to achieve the anticorrosive effect. The commonly used high shielding coatings, such as epoxy cloud iron intermediate paint and epoxy glass flake coating, are such shielding industrial anticorrosive paint. They respectively use mica iron oxide and glass flake as shielding media, which can shield the flow of corrosion factors such as water, oxygen and ions. The flake pigment forms a structure with maze effect, extending the way for the corrosive medium to penetrate the coating. More effective barrier corrosion medium, so as to improve the anticorrosion ability of coating, to achieve excellent anticorrosion effect, to achieve the purpose of anticorrosion.

2. Corrosion inhibition, passivation and corrosion protection

The passivation mechanism is due to the interaction between metals and oxidizing substances, which generates a very thin, dense, good covering performance and firm passivation film adsorbed on the metal surface. It has the effect of completely separating the metal from the corrosive medium to prevent the contact between the metal and the corrosive medium, so that the metal basically stops dissolving, forming a blunt state to achieve the role of corrosion prevention. Through the application of anticorrosive coatings to play the role of corrosion inhibition, the substrate metal can play the role of slowing down the corrosion. The passivation principle can protect the substrate and isolate the corrosive medium. For example, epoxy coal asphalt anticorrosive coating, with the help of anti-rust pigments contained in the coating, corrosion inhibition ions are dissociated in the solution, so that the surface of the matrix passivation, inhibit the corrosion process.

3. Electrochemical corrosion protection

This anticorrosive mechanism is also known as cathodic protection, that is, the principle of sacrificing the anode to protect the cathode, so that the substrate metal is protected, to play the role of anticorrosive coating. Zinc-rich epoxy primer, for example, is an industrial coating that protects steel from corrosion by cathodic protection. Zinc is active metal, zinc and iron contact, in the presence of corrosive medium, the formation of galvanic effect, zinc lose electrons and iron get electrons, iron because of the electron and avoid corrosion, is well protected. In addition to epoxy zinc-rich primer, inorganic zinc-rich primer and cold galvanized paint, all use the cathodic protection of zinc to achieve the purpose of anticorrosion of steel. This type of anticorrosive coating is usually used in areas with high anticorrosive requirements.