The anti-corrosion coating of seamless steel pipe refers to the use of paint to uniformly and densely coat the surface of the rust-removed steel pipe to isolate it from various corrosive media. It is one of the most basic methods for anti-corrosion of seamless pipes. There are many kinds of anti-corrosion coatings, and their properties and uses are different. Among them, the coating technology is to form a continuous covering layer of insulating material on the metal surface to insulate the metal and the electrolyte in direct contact with it.That is to set a high resistance so that the electrochemical reaction cannot occur normally.
Seamless steel pipes means pipes with hollow sections and are used in large quantities for conveying fluids.When transporting oil, natural gas, gas, water and some solid materials, seamless pipes are often affected by external factors such as geological conditions and weather conditions and corrode. Therefore, it is necessary to carry out anti-corrosion of seamless pipes.
Commonly used coatings are as follows
1.Epoxy anti-corrosion coating
Epoxy resin anti-corrosion coatings are widely used for anti-corrosion of inner and outer walls of pipelines, and have the advantages of strong adhesion, acid and alkali resistance, and low shrinkage rate.The disadvantage is that the paint film is easy to powder and has poor weather resistance. Especially when the curing treatment is not good, the water resistance of the coating is poor, and the film is easy to whiten and become brittle.
2.Asphalt anti-corrosion coating
The raw materials of asphalt coating are easy to obtain, the price is low, it is resistant to the corrosion of dilute acid and dilute alkali at room temperature, the paint film dries quickly, and has good elasticity, and is often used as a waterproof layer. Asphalt coating contains hydrocarbon structure, can dissolve in some organic substances, is easy to react and decompose under the condition of strong oxidant, and is not resistant to organic solvents, and will be embrittled at low temperature. Existing styling products, such as coal epoxy coal tar pitch, coal tar enamel paint, and petroleum pitch paint, are all modified bitumen paints to improve the hardness, temperature resistance, weather resistance and adhesion of the paint film. The main purpose of asphalt coating is waterproofing and anti-corrosion of underground pipelines. When used for anti-corrosion of underground pipelines, it is usually covered with glass cloth.
3.Urushiol anti-corrosion coating
Urushiol paint is made of raw lacquer through dehydration and polycondensation and diluted with organic solvent. Compared with raw lacquer, it has less toxicity and quicker drying. Urushiol paint is resistant to acid, alkali, ammonia and water. It can be used as anti-corrosion paint for ammonia gas, ammonia water, chlorine gas and hydrogen sulfide gas, as well as moisture-proof and anti-corrosion paint for underground pipelines.
4.Acrylic or polyurethane anti-corrosion coating
Polyurethane coatings are resistant to acid, alkali, oil, water and abrasion. As anti-corrosion coatings, there are mainly one-component moisture-curing type, two-component catalyst curing type and hydroxyl curing type. In order to improve certain properties, it is often used in combination with epoxy resin, asphalt, etc. The self-made polyurethane asphalt paint has fast curing and good water resistance, and can be used for the anti-corrosion of the inner wall of the pressure water pipeline of the power station and the inner wall of the underground steel pipe of the water injection well in the oil field.
5.Olefin resin anti-corrosion coating
Olefin resin anti-corrosion coatings are mainly made of resins containing ethylene or propylene molecular structure as raw materials, plus modified resins, fillers, etc., and have good water resistance, acid resistance, alkali resistance and weather resistance.
6.Perchloroethylene resin anti-corrosion coating
Perchloroethylene coating is a kind of coating widely used in chemical pipelines to prevent atmospheric corrosion. The disadvantage is that it has poor adhesion with the pipeline. In order to improve its adhesion, epoxy resin is commonly used to modify it, and certain results have been achieved.
7.Chlorinated rubber anti-corrosion coating
The chlorinated rubber obtained by the chlorination reaction of natural rubber or synthetic rubber is dissolved in an organic solvent to obtain a chlorinated rubber coating. Its characteristics are that it is more resistant to the corrosion of dilute acid and dilute alkali, has good permeability resistance, and is flame retardant.
8.High temperature anti-corrosion coating
High-temperature anti-corrosion coatings are mainly silicone resin heat-resistant coatings. The operating temperature can reach 500 ° C. The advantages are good water resistance, corrosion resistance and weather resistance. The disadvantage is that the adhesion is poor, the price is expensive, and the products containing lead powder need to be dried.
9.Zinc-rich anti-corrosion coating
There are two types of zinc-rich coatings: inorganic zinc-rich coatings and organic zinc-rich coatings. Inorganic coatings are composed of zinc powder, sodium silicate (water glass) and curing agent; organic coatings are composed of zinc powder and resin (mainly epoxy resin). The anti-corrosion principle of zinc-rich coatings is mainly that zinc powder can play a cathodic protection role on steel materials, so it is suitable for anti-corrosion of water, seawater, oil and marine atmosphere. Not suitable for use in acid and alkali medium.
10.cement mortar
Cement mortar is mainly used as the lining coating of water supply pipelines, forming a protective film on the inner wall of the pipeline to prevent corrosion caused by direct contact between the medium and the pipeline. Its characteristics are economical and pollution-free. At present, there are modified varieties such as polymer cement mortar, which can be applied to pipelines such as hot water, sea water and sewage, and can inhibit the growth of microorganisms and bryophytes.
Seamless steel pipes means pipes with hollow sections and are used in large quantities for conveying fluids.When transporting oil, natural gas, gas, water and some solid materials, seamless pipes are often affected by external factors such as geological conditions and weather conditions and corrode. Therefore, it is necessary to carry out anti-corrosion of seamless pipes.
Commonly used coatings are as follows
1.Epoxy anti-corrosion coating
Epoxy resin anti-corrosion coatings are widely used for anti-corrosion of inner and outer walls of pipelines, and have the advantages of strong adhesion, acid and alkali resistance, and low shrinkage rate.The disadvantage is that the paint film is easy to powder and has poor weather resistance. Especially when the curing treatment is not good, the water resistance of the coating is poor, and the film is easy to whiten and become brittle.
2.Asphalt anti-corrosion coating
The raw materials of asphalt coating are easy to obtain, the price is low, it is resistant to the corrosion of dilute acid and dilute alkali at room temperature, the paint film dries quickly, and has good elasticity, and is often used as a waterproof layer. Asphalt coating contains hydrocarbon structure, can dissolve in some organic substances, is easy to react and decompose under the condition of strong oxidant, and is not resistant to organic solvents, and will be embrittled at low temperature. Existing styling products, such as coal epoxy coal tar pitch, coal tar enamel paint, and petroleum pitch paint, are all modified bitumen paints to improve the hardness, temperature resistance, weather resistance and adhesion of the paint film. The main purpose of asphalt coating is waterproofing and anti-corrosion of underground pipelines. When used for anti-corrosion of underground pipelines, it is usually covered with glass cloth.
3.Urushiol anti-corrosion coating
Urushiol paint is made of raw lacquer through dehydration and polycondensation and diluted with organic solvent. Compared with raw lacquer, it has less toxicity and quicker drying. Urushiol paint is resistant to acid, alkali, ammonia and water. It can be used as anti-corrosion paint for ammonia gas, ammonia water, chlorine gas and hydrogen sulfide gas, as well as moisture-proof and anti-corrosion paint for underground pipelines.
4.Acrylic or polyurethane anti-corrosion coating
Polyurethane coatings are resistant to acid, alkali, oil, water and abrasion. As anti-corrosion coatings, there are mainly one-component moisture-curing type, two-component catalyst curing type and hydroxyl curing type. In order to improve certain properties, it is often used in combination with epoxy resin, asphalt, etc. The self-made polyurethane asphalt paint has fast curing and good water resistance, and can be used for the anti-corrosion of the inner wall of the pressure water pipeline of the power station and the inner wall of the underground steel pipe of the water injection well in the oil field.
5.Olefin resin anti-corrosion coating
Olefin resin anti-corrosion coatings are mainly made of resins containing ethylene or propylene molecular structure as raw materials, plus modified resins, fillers, etc., and have good water resistance, acid resistance, alkali resistance and weather resistance.
6.Perchloroethylene resin anti-corrosion coating
Perchloroethylene coating is a kind of coating widely used in chemical pipelines to prevent atmospheric corrosion. The disadvantage is that it has poor adhesion with the pipeline. In order to improve its adhesion, epoxy resin is commonly used to modify it, and certain results have been achieved.
7.Chlorinated rubber anti-corrosion coating
The chlorinated rubber obtained by the chlorination reaction of natural rubber or synthetic rubber is dissolved in an organic solvent to obtain a chlorinated rubber coating. Its characteristics are that it is more resistant to the corrosion of dilute acid and dilute alkali, has good permeability resistance, and is flame retardant.
8.High temperature anti-corrosion coating
High-temperature anti-corrosion coatings are mainly silicone resin heat-resistant coatings. The operating temperature can reach 500 ° C. The advantages are good water resistance, corrosion resistance and weather resistance. The disadvantage is that the adhesion is poor, the price is expensive, and the products containing lead powder need to be dried.
9.Zinc-rich anti-corrosion coating
There are two types of zinc-rich coatings: inorganic zinc-rich coatings and organic zinc-rich coatings. Inorganic coatings are composed of zinc powder, sodium silicate (water glass) and curing agent; organic coatings are composed of zinc powder and resin (mainly epoxy resin). The anti-corrosion principle of zinc-rich coatings is mainly that zinc powder can play a cathodic protection role on steel materials, so it is suitable for anti-corrosion of water, seawater, oil and marine atmosphere. Not suitable for use in acid and alkali medium.
10.cement mortar
Cement mortar is mainly used as the lining coating of water supply pipelines, forming a protective film on the inner wall of the pipeline to prevent corrosion caused by direct contact between the medium and the pipeline. Its characteristics are economical and pollution-free. At present, there are modified varieties such as polymer cement mortar, which can be applied to pipelines such as hot water, sea water and sewage, and can inhibit the growth of microorganisms and bryophytes.
Previous：Straightening of LSAW steel tubes
