What are the methods of steel pipe anti-corrosion?

Why steel pipe should be anticorrosion? As the name suggests, steel pipe anticorrosion is to prevent corrosion of steel pipe, reducing the service life. pe anticorrosive steel pipe processing transmission of petroleum, water, natural gas and other pipeline projects, will use the steel pipe as an economic transmission material, but some of the material and chemical elements of the steel pipe decide that it does not have a long term resistance to corrosion, which greatly shortens the service life, regardless of whether it is buried or overhead, will be faced with the problem, then, how to Solve this problem? Later, people invented to the outer wall or inner wall of the steel pipe to do coating anti-corrosion, to effectively control and prevent steel pipe corrosion method.

At present, steel pipe anti-corrosion coatings are mainly:

Grease coating

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

National lacquer

National lacquer, also known as raw lacquer and lacquer, is unique to China. Raw lacquer is a milky-white viscous liquid, which is made by cutting the bark from the lacquer tree and filtering it to remove impurities. When raw lacquer is applied to the surface of an object, the color quickly changes from white to red and from red to purple. If it takes a long time, it can turn into a hard and bright black lacquer film. Chartreuse is the main component of raw lacquer, with a content of 30-70% (the higher the content of chartreuse, the better the quality of raw lacquer). State lacquer has strong adhesion, tough paint film, good luster, soil corrosion resistance, water and oil resistance. The disadvantage is that it is toxic and easy to cause skin allergies. In addition, it is not resistant to strong oxidizing agents, poor alkali resistance.

Phenolic resin coatings

Mainly includes alcohol-soluble phenolic resin, modified phenolic resin, pure phenolic resin and so on. Alcohol-soluble phenolic resin coatings have good corrosion resistance, but its disadvantages are inconvenient construction, poor flexibility, weak adhesion, so its application is limited to some extent. Phenolic resins need to be modified in the process of use. For example, rosin modified phenolic resin and tung oil refining, adding a variety of pigments, grinding can be made into a variety of magnetic coatings. The paint film is tough and inexpensive, and is widely used in the coating of furniture and doors and windows. Pure phenolic resin paint adhesion, water resistance, moisture resistance, heat resistance, corrosion resistance, weather resistance.

Epoxy resin coating

Epoxy coatings have good adhesion, strong adhesion to metal, concrete, wood, glass and other materials, good alkali resistance, good insulation properties. The disadvantage is poor aging resistance. Epoxy anti-corrosion coatings are usually composed of epoxy resin and curing agent. The nature of the curing agent will also affect the performance of the paint film. Epoxy resin coating is a one-component coating system with epoxy resin as the film-forming material. The epoxy resin consists of an epoxy resin and a vegetable oil fatty acid ester. Compared with general epoxy coatings, this coating has the advantages of low cost and poor alkali resistance. Commonly used in chemical plants for a variety of metal primer and outdoor equipment anticorrosive coatings.

Polyurethane coatings

Polyurethane resin for anti-corrosion coatings usually contain two components: isocyanate group - NCO and hydroxyl. Polyurethane (polyurethane) is used in the process of mixing two-component and reaction curing.

Polyurethane coatings have good physical and mechanical properties, paint film hard, flexible, bright, full, wear-resistant, strong adhesion, corrosion-resistant, resistant to oils, acids, chemicals, industrial emissions and other characteristics. Alkali resistance is slightly lower than epoxy coatings; aging resistance is better than epoxy coatings, commonly used as a topcoat, can also be used as a primer; polyurethane resin can be mixed with a variety of resins, can be widely adjusted formulations to meet a variety of requirements for use; curing at room temperature or heating curing, low temperature (0 ℃) can be cured; polyisocyanate component storage stability is poor, it is necessary to isolate the moisture, to avoid freezing. Polyurethane coatings are expensive and have a long service life.

Long fiber winding fiberglass reinforced epoxy lining

The unique embedded lining process is used to form a corrosion-resistant material in the steel pipe. This corrosion-resistant material can isolate oilfield corrosive liquids and gases from the steel pipe, providing an internal anti-corrosion lining system for oilfield steel pipes and pipelines. It is very costly to replace damaged wellbore production tubing or subsea flowlines. It can provide good corrosion protection in very harsh environments, which is unmatched by other products.

Polyethylene and polypropylene resin coatings

Polyethylene resin anticorrosive coatings are film-forming coatings made from monomer resins. Polyethylene coatings have been widely produced and applied. Polyethylene pipeline anticorrosion sealing, high mechanical strength, waterproof, stable quality, easy construction, good applicability, no pollution of the environment. low water absorption of PE (less than 0).01%), high epoxy strength, low water absorption of PE, hot melt adhesive softness, high reliability of anticorrosion. The disadvantage is that the cost is higher than other patching materials. The coating raw material source is abundant, has been widely used in corrosion.

Furan resin coating

Furan resin coatings resistant to a variety of non-oxidizing inorganic acids, electrolyte solutions, a variety of organic solvents, alkali resistance is also prominent, but oxidation resistance is not good. Furan resin series of anticorrosive coatings including furfuryl alcohol coatings, furfuryl acetone formaldehyde coatings and modified furan resin coatings.

Rubber coatings

Rubber anti-corrosion coatings are made of chemically treated or mechanically processed natural rubber or synthetic rubber, with solvents, fillers, pigments, catalysts and so on.

Asphalt coatings

Bitumen is one of the important anti-corrosion coatings. Especially coal tar pitch is the best. Coal tar pitch coatings are inexpensive and have advantages such as water resistance. Immersed in water for ten years, its water absorption rate of only 0.1% - 0.2%; resistance to the erosion of some chemical media; not completely rusted steel surface still has good wettability; high solids content, you can get a thick film; low price. Its disadvantage is brittle in winter and soft in summer. After exposure, some components volatilize and escape, which can crack the paint film. These disadvantages can be improved by adding some other resins. For example, adding chlorinated rubber can improve the drying property of asphalt paint and the disadvantage of brittle in winter and soft in summer; epoxy asphalt paint made of epoxy resin has the advantages of asphalt paint and epoxy paint, and it has achieved very satisfactory results in anticorrosion. Asphalt coatings have been used in the bottom of the container, the bottom of the ship, dock gates, cofferdams and other occasions, with good anti-corrosion effect.

Heavy-duty anti-corrosion coatings

Heavy anti-corrosion coatings relative to ordinary anti-corrosion coatings. It refers to the harsh corrosive conditions, anti-corrosion effect than ordinary corrosion coatings more than several times the anti-corrosion coatings. It is characterized by excellent resistance to corrosive media, outstanding durability, service life of more than a few years. It is mainly used for marine structures and chemical equipment, storage tanks and pipelines.