As an excellent anti-corrosion coating, it must have the following characteristics:
1. Good corrosion resistance: the so-called corrosion resistance of the coating refers to the corrosive medium (such as water, acid, alkali, salt, various chemicals, waste liquid, air, moisture, chemical gas, etc.) that the cured coating is in contact with. ), both in terms of physical and chemical properties are stable, that is, it will not be swelled or dissolved by corrosive media, will not be damaged or decomposed by corrosive media, and will not cause harmful chemical reactions with corrosive media.
2. The air permeability and water permeability should be small: the atmospheric corrosion of steel requires the action of moisture and oxygen, otherwise the corrosion rate can be neglected. The corrosion of painted steel sheet is essentially caused by the penetration of water and oxygen into the interface between the coating film and the metal at a considerable speed. Obviously, the air permeability and water permeability of an excellent corrosion-resistant coating film should be as small as possible. For this reason, it is necessary to choose a film-forming substance with a small air permeability and a coating with a large shielding effect, and increase the number of coating passes to make the coating reach a certain thickness.
3. Good adhesion and certain mechanical strength are required: Whether the coating film can firmly adhere to the metal substrate is one of the key factors for its anti-corrosion effect; in addition, the cured coating film should also have Certain physical and mechanical strength to withstand the stress under working conditions.
In practice, it is often the case that a certain paint variety has good corrosion resistance, and the adhesion and mechanical properties of a single pair of substrates are poor and cannot be applied. In order to solve the contradiction between corrosion resistance and mechanical properties, several coatings are often used in combination. For example: Use paint with good adhesion and certain anti-rust ability as primer, and paint with good corrosion resistance and good interlayer adhesion with primer as top paint. If the adhesion between the primer and the topcoat is not good, the so-called intermediate coating that can firmly connect the primer and the topcoat can be used as the "transition" layer. In this way, an anti-corrosion coating system with good mechanical properties and corrosion resistance can be obtained.
In addition to meeting the main requirements of the above three aspects, the anti-corrosion coating should also have good electrical insulation, resistance to temperature change, and moisture resistance. At the same time, it should be calculated economically and convenient for construction.
