Under what circumstances does a seamless steel pipe need pickling?

Seamless steel pipes (SMLS) need to be pickled in the following circumstances to ensure that their surface quality and performance meet the requirements of subsequent processing or use:

1. Removal of oxide scale
Hot-rolled seamless steel pipes: During the hot rolling process, a layer of oxide scale (mainly composed of Fe₂O₃, Fe₃O₄, etc.) will form on the surface of the steel pipe. Pickling can effectively remove this layer of oxide scale and expose a clean metal surface.

2. Remove rust

During storage or transportation: Steel pipes may rust due to exposure to a humid environment during storage or transportation. Pickling can remove rust and restore the surface to a smooth finish.

3. Improve surface quality
Subsequent processing requirements: Before subsequent processing such as cold drawing, cold rolling, galvanizing, and painting, it is necessary to ensure that the surface of the steel pipe is free of oxide scale, rust, and other impurities to improve processing quality and yield rate.

4. Enhance corrosion resistance
Passivation treatment: In some applications, passivation treatment is required after pickling to form a dense oxide film on the surface of the steel pipe to further improve its corrosion resistance.

5. Meet industry standards
Specific industry requirements: For example, industries such as petroleum, natural gas, chemicals, food, and pharmaceuticals have strict requirements on the surface cleanliness and corrosion resistance of steel pipes. Pickling is an important step to meet these standards.

6. Improve coating adhesion
Pre-coating treatment: Before pipe coating, pickling can remove surface impurities, improve the adhesion and uniformity of the coating, and extend the service life of the coating.

7. Pre- and post-welding treatment
Before welding: Remove the oxide scale and rust in the welding area to ensure welding quality.
After welding: Remove the oxide scale and welding slag generated during welding to improve the appearance and corrosion resistance of the weld area.

8. Special application occasions
High-precision pipes: For example, high-precision seamless steel pipes used in aerospace, precision instruments and other fields require extremely high surface quality, and pickling is an indispensable process.

9. Repair and refurbishment
Repair of old pipes: For old steel pipes that have rusted and contaminated after a period of use, they can be repaired and refurbished by pickling to restore their performance.

10. Environmental protection and hygiene requirements

Food and pharmaceutical industry: Steel pipes used to transport food and medicines require extremely high cleanliness and hygiene standards. Pickling can ensure that the surface is free of contamination and meets relevant regulatory requirements.

Read more: Seamless steel pipe pickling process or Carbon steel vs Stainless steel