Why should the steel pipe be anti-corrosion, and what is the use of the anti-corrosion steel pipe?

Why should steel pipes be anti-corrosion? As the name suggests, steel pipe anti-corrosion is to prevent steel pipe corrosion and reduce the service life. PE anti-corrosion steel pipe processing and transportation of oil, water, natural gas and other pipeline projects, will use steel pipe as an economic transmission material, but some steel pipe material and chemical elements determine that it does not have long-term corrosion resistance, thereby greatly shortening the service life, whether buried or overhead, will face this problem, then, how to solve this problem? Later, people invented the outer wall or inner wall of the steel pipe to make a coating anti-corrosion method to effectively control and prevent the corrosion of the steel pipe.

At present, the steel pipe anti-corrosion coatings mainly include:

1. Oil and grease coating

Oil coating is a kind of coating with dry oil as the main film-forming material. It is characterized by convenient production, good brushability, good wettability, low price and flexible paint film; However, the paint film dries slowly, the film is soft, the mechanical properties are poor, the acid and alkali resistance is poor, the water resistance is poor, and the resistance to organic solvents is poor. Dry oil is usually combined with anti-rust pigments to form anti-rust paint, which is used in atmospheric environments and has low corrosion resistance.

2. National paint

National lacquer, also known as raw lacquer and lacquer lacquer, is unique to China. Raw lacquer is a milky white viscous liquid made by cutting the bark from the sumac tree and filtering it to remove impurities. After the raw lacquer is applied to the surface of the object, the color quickly changes from white to red and from red to purple. If it takes a long time, it can become a hard and bright black paint film. Urushiol is the main component of raw lacquer with a content of 30-70% (the higher the urushiol content, the better the quality of raw lacquer). The national paint has strong adhesion, tough paint film, good gloss, soil corrosion resistance, water resistance and oil resistance. 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.

3. phenolic resin coating

It mainly includes alcohol-soluble phenolic resin, modified phenolic resin, pure phenolic resin, etc. Alcohol-soluble phenolic resin coatings have good corrosion resistance, but their disadvantages are inconvenient construction, poor flexibility, and weak adhesion, so their application is limited to a certain extent. Phenolic resins need to be modified during use. For example, rosin modified phenolic resin is refined with tung oil, various pigments are added, and various magnetic coatings can be made after grinding. The paint film is tough and inexpensive, and it is widely used in the coating of furniture and doors and windows. Pure phenolic resin coating has strong adhesion, good water resistance, moisture resistance, heat resistance, corrosion resistance and weather resistance.

4. Epoxy resin coating

Epoxy coating has good adhesion, strong adhesion to metal, concrete, wood, glass and other materials, good alkali resistance and good insulation performance. The disadvantage is poor aging resistance. Epoxy anti-corrosion coatings usually consist of epoxy resin and curing agent. The properties of the curing agent also affect the performance of the paint film. Epoxy resin coating is a one-component coating system that uses epoxy resin as a film-forming material. Epoxy resin consists of epoxy resin and vegetable oil fatty acid esters. Compared with general epoxy coatings, this coating has the advantages of low cost and poor alkali resistance. It is commonly used in various metal primers and outdoor equipment anti-corrosion coatings in chemical plants.

5. Polyurethane coatings

Polyurethane resins used in anti-corrosion coatings typically contain two components: isocyanate-based -NCO and hydroxyl. Polyurethane (polyurethane) is a two-component mixture during use and react-cured.

Polyurethane coatings have the characteristics of good physical and mechanical properties, hard paint film, flexibility, brightness, fullness, wear resistance, strong adhesion, corrosion resistance, oil resistance, acid resistance, chemicals, industrial waste gas, etc. Alkali resistance is slightly lower than epoxy coatings; Aging resistance is better than epoxy coatings, often used as a topcoat, can also be used as a primer; Polyurethane resin can be mixed with various resins, and the formulation can be widely adjusted to meet various use requirements; Room temperature curing or heat curing, low temperature (0 °C) can also cure; Polyisocyanate components have poor storage stability and must be isolated from moisture to avoid freezing. Polyurethane coatings are expensive and have a long service life.

6. Long fiber winding FRP reinforced epoxy lining

A unique embedded lining process is used to form a corrosion-resistant material in the steel pipe. This corrosion-resistant material isolates oilfield corrosive liquids and gases from steel pipes, providing an internal anti-corrosion lining system for oilfield steel pipes and pipelines. For damaged bottom production tubing or subsea streamlines, the replacement cost is very high. It can provide good corrosion resistance protection in very harsh environments, which is unmatched by other products.

7. Polyethylene, polypropylene resin coatings

Polyethylene resin anti-corrosion coatings are film-forming coatings made of monomer resins. Polyethylene coatings have been widely produced and applied.

Polyethylene pipeline has strong anti-corrosion sealing, high mechanical strength, strong waterproofness, stable quality, convenient construction, good applicability, and does not pollute the environment. PE has low water absorption (less than 0).01%), high epoxy strength, low PE water absorption, good softness of hot melt adhesive, and high anti-corrosion reliability. The disadvantage is that the cost is higher than other mending materials. The coating has abundant raw materials and has been widely used in corrosion.

Furan resin coatings

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

9. Rubber coatings

Rubber anti-corrosion coatings are made of chemically treated or mechanically processed natural rubber or synthetic rubber, with the addition of solvents, fillers, pigments, catalysts, etc.

10. Bitumen coating

Bitumen is one of the important anti-corrosion coatings. In particular, coal coke bitumen is better. Coal coke