LSAW Steel Pipe, or straight seam submerged arc welded steel pipe, has the advantages of good weld quality and strong pressure bearing capacity. It is widely used in petrochemical, construction engineering, automobile manufacturing and other fields. The following is an analysis of common anti-corrosion treatment methods for LSAW steel pipes in different application environments:

Petrochemical industry

Environmental characteristics: The transported media are mostly corrosive substances such as oil, gas, acid, alkali, etc., and the working pressure and temperature change range is large, and the soil environment in which the pipeline is located is also relatively complex.

Anti-corrosion treatment method

Coating anti-corrosion: Epoxy resin coating, polyurethane coating, etc. are often used. These coatings have good chemical corrosion resistance, water resistance and mechanical strength, and can effectively prevent corrosive media from penetrating into the surface of the steel pipe. For example, in pipelines for transporting crude oil, epoxy resin coatings can resist the corrosion of sulfides, organic acids, etc. in crude oil to steel pipes.

3PE anti-corrosion: that is, a three-layer polyethylene anti-corrosion structure, consisting of epoxy powder at the bottom layer, adhesive at the middle layer and polyethylene at the outer layer. This anti-corrosion structure has excellent corrosion resistance, wear resistance and soil stress resistance, and is suitable for long-distance oil and gas pipelines.

Cathodic protection: usually using sacrificial anode method or impressed current method. In petrochemical pipelines, anti-corrosion coatings are often used in combination with cathodic protection to achieve better anti-corrosion effects. For example, in some coastal areas, oil pipelines have high water content, high salt content and strong corrosiveness in the soil. The combination of sacrificial anode method cathodic protection and coating anti-corrosion can effectively extend the service life of the pipeline.

Construction Engineering Field

Environmental Characteristics: When used in building water supply and drainage systems, the media in contact are mainly water, including tap water, sewage, etc.; when used for gas transportation, the pipeline needs to be buried and will be corroded by moisture and salt in the soil.

Anti-corrosion treatment method

Hot-dip galvanizing: Immerse the steel pipe in molten zinc liquid to form a layer of zinc coating on the surface of the steel pipe. The zinc coating has good corrosion resistance and decorative properties, and can effectively prevent the steel pipe from rusting in a humid environment. In building water supply and drainage pipelines, hot-dip galvanized steel pipes are widely used, which can improve the corrosion resistance of the pipeline and ensure water quality safety.

Epoxy coal tar coating: has excellent adhesion and water resistance, and the price is relatively low. In the construction sewage discharge pipe, the epoxy coal tar coating can resist the corrosion of the steel pipe by the acid and alkali substances in the sewage.

Cement mortar lining: mainly used for anti-corrosion in steel pipes for conveying drinking water and water supply. The cement mortar lining can prevent water from directly contacting the inner wall of the steel pipe, play an isolation and protection role, and at the same time reduce the friction resistance in the pipe and improve the water delivery efficiency.

Automobile manufacturing industry

Environmental characteristics: LSAW steel pipes for automobiles are mainly used to manufacture automobile chassis, exhaust systems and other components. They need to withstand the vibration, impact and external environment during vehicle driving, such as rain, snow, salt, etc.

Anti-corrosion treatment method

Galvanizing treatment: including electrogalvanizing and hot-dip galvanizing. The galvanized layer can improve the corrosion resistance and decorativeness of the steel pipe and prevent the steel pipe from rusting in a humid environment. For example, after the steel pipe in the chassis of the car is galvanized, it can effectively resist the corrosion of the chassis by water and salt on the road surface, and extend the service life of the car.

Painting treatment: Generally, coatings with good weather resistance, such as acrylic paint, polyurethane paint, etc., are used. Painting can form a protective film on the surface of the steel pipe, isolating air and moisture, and can also serve as a decoration. The steel pipes in the exhaust system of the car are usually coated with high temperature resistant and weather resistant coatings to resist the erosion of high temperature exhaust gas and the external environment.

In addition to the above-mentioned factors such as medium, pressure, temperature, etc., the following environmental factors will also affect the anti-corrosion treatment of LSAW steel pipes:

Geographic environment

Soil characteristics: The soil properties in different regions vary greatly, such as the pH, water content, air permeability of the soil, and the microorganisms contained in the soil, which will affect the corrosion rate of the steel pipe. For example, in acidic soil, steel pipes are prone to hydrogen evolution corrosion, and it is necessary to use an acid-resistant anti-corrosion coating or increase the strength of cathodic protection.

Altitude: The air is thin, the air pressure is low, and the temperature difference between day and night is large in high altitude areas. The anti-corrosion coating on the surface of the steel pipe is easily affected by thermal stress and cracks or falls off. Therefore, the anti-corrosion coating of LSAW steel pipes used in high-altitude areas needs to have good thermal stress resistance and weather resistance.

Topography: In mountainous or hilly areas, steel pipes may be affected by greater soil stress and rock friction, which can easily lead to damage to the anti-corrosion layer. For steel pipes in this terrain environment, it is necessary to use an anti-corrosion coating with high mechanical strength and wear resistance, or take additional protective measures, such as adding protective pads or casings.

Climate conditions

Humidity: Air humidity is one of the important factors affecting the corrosion of steel pipes. When the air humidity is high, a water film is easily formed on the surface of the steel pipe, which accelerates the corrosion process. In a humid environment, it is necessary to select an anti-corrosion coating with good moisture resistance, such as a silicone coating, to prevent moisture from penetrating into the surface of the steel pipe.

Precipitation: Frequent precipitation will cause the anti-corrosion coating on the surface of the steel pipe to be eroded, reducing the protective performance of the coating. At the same time, rainwater may contain acidic substances or other pollutants, which will cause corrosion to the steel pipe. For steel pipes that are often eroded by rainwater, it is necessary to regularly inspect and maintain the anti-corrosion coating, and if necessary, select a coating material with good water resistance and erosion resistance.

Sunlight: Long-term sunlight will increase the surface temperature of the steel pipe and accelerate the aging and degradation of the anti-corrosion coating. In areas where direct sunlight is exposed for a long time, an anti-corrosion coating with good UV resistance, such as fluorocarbon coating, should be selected to extend the service life of the coating.

Industrial environment

Air pollution: In industrially intensive areas, the air may contain a large amount of pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter. These pollutants will combine with moisture in the air to form acidic substances, causing corrosion to the steel pipe. The anti-corrosion coating of LSAW steel pipes in this type of environment needs to have good acid and alkali resistance.

Industrial wastewater: If there is industrial wastewater discharge around the steel pipe, the heavy metal ions, acid and alkali substances and organic pollutants in the wastewater will corrode the steel pipe. At this time, it is necessary to select a suitable anti-corrosion treatment method according to the specific composition of the wastewater, such as using a chemical corrosion-resistant coating or performing special surface treatment on the steel pipe.

Electromagnetic environment: In some industrial sites, such as substations and electrolysis workshops, there is a strong electromagnetic field. The electromagnetic field may affect the electrochemical process on the surface of the steel pipe and accelerate corrosion. For steel pipes in this type of electromagnetic environment, in addition to taking conventional anti-corrosion measures, it may be necessary to consider auxiliary measures such as electromagnetic shielding to reduce the impact of electromagnetics on corrosion.