You are here: Home » News » Industry News » Main types of anti-corrosion coatings for large diameter spiral steel pipelines

Main types of anti-corrosion coatings for large diameter spiral steel pipelines

Views: 1    

Anti-corrosion of large-diameter spiral steel pipelines means that when large-diameter spiral steel pipelines are used and transported, the pipelines are affected by the use environment and the transportation medium, causing chemical or electrochemical reactions to cause corrosion of the pipelines. In order to effectively prevent or control corrosion of large-diameter spiral steel pipelines, scientists are seeking a new, higher and more effective method.

1. Grease coating - used in atmospheric environments with low corrosion resistance requirements. Grease paint is a type of paint that uses dry oil as the main film-forming substance. It is characterized by easy production, good brushability, good wettability to the surface, low price, and flexible paint film; however, the paint film dries slowly, is soft, has poor mechanical properties, and is resistant to acid and alkali, water and water. Poor organic solvent resistance. Dry oil is often combined with anti-rust pigments to form anti-rust paint, which is used in atmospheric environments with low corrosion resistance requirements.

2. National lacquer: Raw lacquer, also known as raw lacquer and lacquer, is a specialty of my country. Raw lacquer is a milky white viscous liquid that flows out from the bark of the growing lacquer tree. It is filtered through fine cloth to remove impurities. After it is painted on the surface of an object, its color quickly changes from white to red, and from red to purple. After a long time, it can turn into a hard and shiny black paint film. 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 the raw paint. National paint has strong adhesion, tough paint film and good gloss. It is resistant to soil corrosion, water and oil. The disadvantage is that it is toxic and can easily cause skin allergies. In addition, it is not resistant to strong oxidants and has poor alkali resistance. There are now many modified raw lacquer coatings that overcome the above shortcomings to varying degrees.

3. Phenolic resin coatings: mainly include 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, have poor flexibility and adhesion, and their applications are subject to certain limitations. Therefore, it is often necessary to modify phenolic resins. For example, rosin-modified phenolic resin is refined with tung oil, various pigments are added, and various enamels can be produced after grinding. The paint film is tough and cheap, and is widely used in the coating of furniture, doors and windows. Pure phenolic resin coating has strong adhesion, water resistance, humidity and heat resistance, corrosion resistance and good weather resistance.

4. Epoxy resin coating: 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 its anti-aging properties are poor. Epoxy anti-corrosion coatings usually consist of two components: epoxy resin and curing agent. The nature of the curing agent also affects the performance of the paint film. Commonly used curing agents include: ① Fatty amines and their modifications. The characteristic is that it can be cured at room temperature, and unmodified fatty amines are more toxic. ②Aromatic amines and their modifications. It is characterized by slow reaction, often requires heating and solidification, and has weak toxicity. ③Polyamide resin. It is characterized by good weather resistance, low toxicity, good elasticity and slightly poor corrosion resistance. ④Phenolic resin, urea-formaldehyde resin and other synthetic resins. These resins and epoxy resins are baked at high temperatures and then cross-linked 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 using epoxy ester resin as a film former. Epoxy ester resin is composed of epoxy resin and vegetable oil fatty acid ester. Compared with general epoxy coatings, this coating has lower cost and poorer alkali resistance. Commonly used as various metal primers and anti-corrosion paint for outdoor equipment in chemical plants.

5. Polyurethane coating: Polyurethane resin used in anti-corrosion coatings often contains two components: isocyanate group-NCO and hydroxyl group. When used, the two components are mixed and reacted to solidify to form polyurethane (polyurethane). Characteristics of polyurethane coatings: ① Good 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 gases. The alkali resistance is slightly lower than that of epoxy coatings. ③The aging resistance is better than that of epoxy coatings. Often used as a topcoat, it can also be used as a primer. ④ Polyurethane resin can be miscible with a variety of resins, and the formula can be adjusted within a wide range to meet various usage requirements. ⑤Can be cured at room temperature or heated, and can also be cured at lower temperatures (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.

6. Polyethylene and polypropylene resin coatings: Polyethylene resin anti-corrosion coatings are coatings in which the resin is a film-forming substance made of a monomer. Among them, polyethylene coatings have been produced and applied in large quantities. Polyethylene pipes have strong anti-corrosion and sealing properties, high mechanical strength, strong waterproofing, stable quality, convenient construction, good applicability, and do not pollute the environment. PE has low water absorption (less than 0.01%), high epoxy strength, low PE water absorption and good hot melt adhesive softness, etc. It has high anti-corrosion reliability. The disadvantage is: compared with the cost of other repairing materials ,costly. The raw materials of this coating are rich in sources and have been widely used in corrosion.

7. Furan resin coating: Furan resin coating is resistant to various non-oxidizing inorganic acids, electrolyte solutions, and various organic solvents. Its alkali resistance is also outstanding, but its oxidation resistance is not good. Furan resin series anti-corrosion coatings include furfuryl alcohol resin coatings, furfural acetone formaldehyde resin coatings and modified furan resin coatings.

8. Rubber coatings: Rubber anti-corrosion coatings are made of chemically or mechanically processed natural rubber or synthetic rubber as film-forming substances, plus solvents, fillers, pigments, catalysts, etc. ⑴Chlorinated rubber coating. The coating has good water resistance, resistance to salt water and salt spray; it has certain acid and alkali corrosion resistance, and can withstand 10% HCl, H2SO4, HNO3, different concentrations of NaOH and wet Cl2 below 50°C. But it is not resistant to solvents and has poor aging resistance and heat resistance. This coating is widely used in ships, ports, chemical industry and other places. ⑵Neoprene coating. The coating is resistant to ozone and chemicals, has outstanding alkali resistance and good weather resistance; it is oil and heat resistant and can be made into a peelable coating. The disadvantage is that the storage stability is poor; the coating is easy to change color and is not easy to make white or light-colored paint. ⑶Chlorosulfonated polyethylene rubber coating. It is produced by reacting polyethylene resin with chlorine and sulfur dioxide (or chlorosulfonic acid). The coating has excellent ozone resistance, significant weather resistance, low water absorption, oil resistance, and temperature resistance. It can be used above 120°C and does not become brittle at -50°C.

9. Asphalt coating: Asphalt is an important anti-corrosion coating. Especially coal tar pitch, coal tar pitch coating is cheap and has the following advantages: ① Water resistance, its water absorption rate is only 0.1% to 0.2% after being immersed in water for 10 years; ② Resistant to the erosion of some chemical media; ③ For future use The fully derusted steel surface still has good wettability; ④ The solid content is high, and a thick film can be obtained; ⑤ The price is low. Its disadvantage is that it becomes brittle in cold winter and soft in summer heat. After exposure, some components volatilize and escape, which will cause the paint film to crack. These shortcomings can be improved by adding some other resins. For example, adding chlorinated rubber can improve the dryness of asphalt coatings and improve the shortcomings of brittleness in winter and softness in summer; epoxy asphalt coatings made by adding epoxy resin can combine the advantages of asphalt coatings and epoxy coatings, and gain advantages in anti-corrosion. Very satisfied with the results. Asphalt coatings have been used on container bottoms, ship bottoms, dock gates, cofferdams, etc., and have very good anti-corrosion effects.

10. Heavy-duty anti-corrosion coating: Heavy-duty anti-corrosion coating is compared to general anti-corrosion coating. It refers to an anti-corrosion coating whose anti-corrosion effect is several times higher than that of general corrosion coatings under severe corrosive conditions. It is characterized by excellent resistance to strong corrosive media, outstanding durability, and a service life of more than several years. Mainly used in marine structures and chemical equipment, storage tanks and pipelines.




  Hunan Gaoxing Steel Development Zone, No.1888 Purui South Rd, Wangcheng District,Changsha, Hunan, China

Tel: 0086-0731-88739521

Copyright  2020 Threeway Steel Co.,Ltd. All Rights Reserved