The national standard spiral steel pipe refers to the steel pipe that is used and transported as a medium, and the steel pipe is corroded by chemical or electrochemical reactions due to the influence of the use environment and the conveying medium. The quality of the coating construction has a great influence on the performance of the coating. In the actual coating process, there are many examples where the expected anti-corrosion effect cannot be achieved due to improper construction methods. In particular, many anti-corrosion coatings with excellent performance are extremely sensitive to construction methods. Only when construction is carried out in strict accordance with their respective construction conditions can they form a normal coating and achieve the expected anti-corrosion protection effect.
1. Grease coating
Grease coatings are a class of coatings with drying oil as the main film-forming material. It is characterized by easy production, good brushability, good wettability to the object surface, low price, and flexible paint film; but the paint film dries slowly, the film is soft, and the mechanical properties are poor. Acid and alkali resistance, water resistance and resistance Poor organic solvent. Drying oils are often combined with anti-rust pigments to form anti-rust paints, which are used in atmospheric environments where corrosion resistance is not high.
2. National paint
Raw lacquer, also known as raw lacquer and lacquer, is one of our specialties. Raw lacquer is a milky white viscous liquid that flows out from the bark of a growing sumac tree. It is filtered through a fine cloth to remove impurities. After it is coated on the surface of the object, the color quickly changes from white to red, from red to purple, and becomes a hard and bright black paint film for a long time.
Urushiol is the main component of raw lacquer, with a content of 30% to 70%. Generally speaking, the higher the urushiol content, the better the quality of raw lacquer.
The national paint has strong adhesion, tough paint film and good gloss. It is resistant to soil corrosion, and is more resistant to water and oil. The disadvantage is that it is toxic and easy to cause skin allergies. In addition, it is not resistant to strong oxidants and has poor alkali resistance.
2. Phenolic resin coating
There are mainly alcohol-soluble phenolic resin, modified phenolic resin, pure phenolic resin, etc. Alcohol-soluble phenolic resin coatings have good corrosion resistance, but they are inconvenient to construct, and their flexibility and adhesion are not very good, so their applications are limited. Therefore, it is often necessary to modify phenolic resins. For example, rosin-modified phenolic resin and tung oil are refined, and various pigments are added. After grinding, various enamels can be obtained. The paint film is tough and inexpensive. It is widely used in furniture, doors and windows. Pure phenolic resin coating has strong adhesion, water resistance, humidity resistance, corrosion resistance and good weather resistance.
3. Epoxy resin coating
National standard spiral steel pipe anti-corrosion
Epoxy coating has good adhesion, and has excellent adhesion to metal, concrete, wood, glass, etc.; it is resistant to alkali, oil and water, and has excellent electrical insulation properties. But the aging resistance is poor. Epoxy anti-corrosion coatings usually consist of two components: epoxy resin and curing agent. The nature of the curing agent also affects the properties of the paint film. Commonly used curing agents are:
①Aliphatic amines and their modifications. The characteristic is that it can be cured at room temperature, and the unmodified aliphatic amine is more toxic.
② Aromatic amines and their modifications. The characteristic is that the reaction is slow, and it often needs to be heated and cured, and the toxicity is weak.
③ Polyamide resin. It is characterized by good weather resistance, low toxicity, good elasticity and slightly poor corrosion resistance.
④ Other synthetic resins such as phenolic resin and urea-formaldehyde resin. These resins and epoxy resins are cross-linked after baking at high temperature to form a film. The paint film has outstanding corrosion resistance, good mechanical properties and decorative properties.
Epoxy ester resin coating is a one-component coating system with epoxy ester resin as film former. Epoxy ester resin is composed of epoxy resin and vegetable oil fatty acid ester. Compared with general epoxy coatings, the coating has lower cost and poor alkali resistance. It is often used as a variety of metal primers and anti-corrosion paints for outdoor equipment in chemical plants.
4. Polyurethane coating
Polyurethane resins used in anti-corrosion coatings often contain two components: isocyanate groups – NCO and hydroxyl groups. When used, the two components are mixed and cured by reaction to form polyurethane (polyurethane).
Features of Polyurethane Coatings:
①Good physical and mechanical properties. The paint film is hard, flexible, bright, plump, wear-resistant and has strong adhesion.
②Excellent corrosion resistance. Resistant to oils, acids, chemicals and industrial waste. Alkali resistance is slightly lower than epoxy coatings.
③The aging resistance is better than epoxy coatings. Often used as a topcoat, but also as a primer.
④Polyurethane resin can be miscible with various resins, and the formula can be adjusted in a wide range to meet various application requirements. ⑤ It can be cured at room temperature or by heating, and it can also be cured when the temperature is low (0℃). ⑥ The storage stability of polyisocyanate components is poor, and moisture must be isolated to avoid jelly. Polyurethane coatings are expensive but have a long service life.