With the continuous development of China's economy, the country is vigorously developing the energy industry. Long distance oil and gas pipelines are an important way to ensure energy security. In the anti-corrosion construction process of oil (gas) pipelines, the surface treatment of steel pipes is one of the key factors determining the service life of pipeline anti-corrosion. It is a prerequisite for whether the polyethylene anti-corrosion tape anti-corrosion layer can be firmly combined with the steel pipes. After verification by research institutions, the service life of anti-corrosion coatings depends not only on factors such as coating type, coating quality, and construction environment, but also on the surface treatment of steel pipes, which accounts for about 50% of the service life. Therefore, it is necessary to strictly follow the requirements of anti-corrosion coating specifications for steel pipe surfaces, continuously explore and summarize, and continuously improve the surface treatment methods of steel pipes.

1 Cleaning

Using solvents and emulsions to clean the surface of steel to remove oil, grease, dust, lubricants, and similar organic substances, but it cannot remove rust, oxide skin, welding flux, etc. on the surface of steel. Therefore, it is only used as an auxiliary means in anti-corrosion production.

2 Tools for rust removal

Mainly using tools such as wire brushes to polish the surface of steel, it can remove loose or raised oxide skin, rust, welding slag, etc. Manual tools can achieve Sa2 level rust removal, while power tools can achieve Sa3 level rust removal. If the steel surface is firmly adhered with oxide scale, the rust removal effect of the tools is not ideal, and the anchor depth required for anti-corrosion construction cannot be achieved.

3 Pickling

Generally, two methods, chemical and electrolytic, are used for pickling treatment. Chemical pickling is only used for pipeline anti-corrosion, which can remove oxide scale, rust, and old coatings. Sometimes, it can be used as a pre-treatment after sandblasting and rust removal. Although chemical cleaning can achieve a certain level of cleanliness and roughness on the surface, its anchor lines are shallow and can easily cause environmental pollution.

4 Spray (Throw) Rust Removal

Spray (blasting) rust removal is achieved by using a high-power motor to drive the high-speed rotation of the spray (blasting) blades, causing abrasives such as steel sand, steel shot, iron wire segment, and minerals to spray (blasting) the surface of the steel pipe under centrifugal force. This not only completely removes rust, oxides, and dirt, but also achieves the required uniform roughness of the steel pipe under the strong impact and friction of the abrasive. After spraying (throwing) rust removal, not only can the physical adsorption on the surface of the pipe be expanded, but also the mechanical adhesion between the anti-corrosion layer and the surface of the pipe can be enhanced. Therefore, spraying (throwing) rust removal is an ideal rust removal method for pipeline anti-corrosion. Generally speaking, shot blasting (sand) rust removal is mainly used for inner surface treatment of pipes, while shot blasting (sand) rust removal is mainly used for outer surface treatment of pipes. Several issues should be noted when using spray (throwing) to remove rust.

4.1 Rust removal level

For the construction process of commonly used anti-corrosion coatings such as epoxy, ethylene, and phenolic for steel pipes, it is generally required that the surface of the steel pipe reach near white level (Sa2.5). Practice has proven that using this rust removal level can almost remove all oxide skin, rust, and other dirt, with anchor depth reaching 40-100 μ m. Fully meet the adhesion requirements between the anti-corrosion layer and the steel pipe, and the spray (throwing) rust removal process can achieve near white level (Sa2.5) technical conditions with lower operating costs and stable and reliable quality.

4.2 Spray (eject) abrasive

In order to achieve the desired rust removal effect, the surface of the steel pipe should be treated according to the