Introduction to rust removal of LSAW steel pipes

In the anti-corrosion construction process for oil and gas pipelines, the surface treatment of LSAW (Longitudinal Submerged Arc Welded) steel pipes is a critical factor that directly influences the service life of the pipeline's anti-corrosion layer. Proper surface treatment ensures a strong bond between the anti-corrosion layer and the steel pipe. According to research, the durability of the anti-corrosion layer depends on factors such as the type of coating, application process, and construction environment. Among these, surface treatment accounts for approximately 50% of the anti-corrosion layer's performance.

Thus, strict adherence to anti-corrosion specifications for the surface of LSAW steel pipes is essential. Continuous improvement of surface treatment methods is equally important. The main rust removal methods for LSAW steel pipes include:

Cleaning
Solvents and emulsions are used to clean the pipe surface, removing oil, grease, dust, lubricants, and similar organic contaminants. However, this method does not eliminate rust, scale, or welding residue and serves only as an auxiliary step in anti-corrosion operations.

Pickling
Chemical and electrolytic pickling methods are employed, with chemical pickling being more commonly used in pipeline anti-corrosion. This process removes oxide scales, rust, and old coatings. It is occasionally used as a secondary treatment after sandblasting. While chemical cleaning achieves high cleanliness and surface roughness, it creates a shallow anchor pattern and may pollute the surrounding environment.

Tool Rust Removal
Tools such as wire brushes are used to remove loose oxide scales, rust, and welding slag from the pipe surface. Manual tool rust removal can achieve a Sa2 level, while power tools can reach Sa3. However, if the oxide scale is firmly adhered to the pipe surface, this method may not achieve the required anchor pattern depth for effective anti-corrosion treatment.

Spraying Rust Removal
Spraying rust removal involves using a high-power motor to drive spray blades, propelling abrasives like steel shot, steel sand, wire fragments, and minerals onto the pipe surface under strong centrifugal force. This method not only removes rust, oxides, and dirt but also achieves the desired uniform surface roughness through the abrasive's impact and friction.

After spraying, the physical adsorption capacity of the steel surface increases, and the mechanical adhesion between the anti-corrosion layer and the pipe surface improves. As such, spraying rust removal is considered an ideal method for anti-corrosion pipeline construction.

Typically, shot peening is employed for internal surface treatment, while shot blasting is used for the external surface of LSAW steel pipes.