Seamless steel pipe pickling process

What is pickling of seamless steel pipe?

Pickling of seamless steel pipe (SMLS pipe) is mainly based on the principle of chemical reaction. The acid reacts with the oxides, rust and other impurities on the surface of the steel pipe to dissolve or peel them off to achieve the purpose of cleaning the surface. The following is the detailed principle of the pickling process:

1. Chemical reaction
The pickling liquid (usually hydrochloric acid or sulfuric acid) reacts chemically with the iron oxide (Fe₂O₃, Fe₃O₄, etc.) on the surface of the steel pipe to generate water-soluble iron salts and hydrogen. The main reactions are as follows:

Hydrochloric acid pickling:

Fe₂O₃ + 8HCl→2FeCl₃+ FeCl₂ + 4H₂O

Sulfuric acid pickling:

2. Physical action

The acid not only dissolves the oxide through chemical reaction, but also helps to peel off the oxide scale and impurities on the surface through physical action (such as the flushing of bubbles). The hydrogen bubbles produced in the reaction will produce mechanical impact on the oxide layer and accelerate its shedding.

3. Surface cleaning
After pickling, the oxide scale, rust and other impurities on the surface of the steel pipe are dissolved or peeled off, revealing a clean metal surface. Subsequently, the residual acid and reaction products are removed by water washing and neutralization to ensure that the surface is free of pollution.

4. Passivation (optional)
In some cases, passivation treatment is performed after pickling to form a dense oxide film on the surface of the steel pipe to further improve its corrosion resistance.

Key factors:

Acid concentration: Too high a concentration may cause excessive corrosion, while too low a concentration may result in poor cleaning effect.
Temperature: Properly increasing the temperature can accelerate the reaction, but too high a temperature will increase acid mist and energy consumption.
Time: Too short a time will result in incomplete cleaning, while too long a time may damage the substrate.

Through the above principles, the pickling process can effectively clean the surface of seamless steel pipes, providing a good foundation for subsequent processing and use.

Pickling process of seamless steel pipes:

The pickling process of seamless steel pipes is mainly used to remove surface oxide scale, rust and other impurities to improve surface quality. The following are the main steps:

1. Pretreatment
Degreasing: Use alkaline solution or organic solvent to remove oil stains on the surface of the steel pipe.
Water washing: Rinse with clean water to ensure that there is no residue on the surface.

2. Pickling
Pickling solution preparation: Commonly used hydrochloric acid or sulfuric acid, the concentration and temperature are adjusted according to the material and degree of oxidation.
Pickling operation: Immerse the steel pipe in the pickling solution, and the time is determined according to the thickness of the oxide scale and the concentration of the acid solution.
Water washing: Rinse with clean water immediately after pickling to remove residual acid.

3. Neutralization
Neutralization treatment: Use alkaline solution (such as sodium carbonate) to neutralize residual acid to prevent corrosion.
Water washing: Rinse with clean water again to ensure that there is no residual neutralizing liquid on the surface.

4. Post-treatment
Passivation treatment: Some steel pipes need to be passivated to form a protective film to enhance corrosion resistance.
Drying: Ensure that there is no water stain on the surface by drying or natural drying.

5. Inspection and packaging
Inspection: Check the surface quality to ensure that there are no defects.
Packaging: Anti-rust packaging is carried out after passing the test for easy storage and transportation.

Precautions:

Safety protection: Operators need to wear protective equipment to avoid acid damage.
Environmental protection: Waste acid needs to be discharged after treatment to meet the standards to prevent environmental pollution.

Through these steps, the surface quality of seamless steel pipes is significantly improved to meet the requirements of subsequent processing and use.

In what fields is steel pipe pickling commonly used?

The steel pipe pickling process is widely used in many fields, mainly used to clean and improve the surface quality of steel pipes to meet the needs of different industries. The following are the main application areas:

1. Oil and gas industry
Oil well pipe: used for oil well drilling and mining, pickling can remove oxide scale and rust, ensure smooth surface and improve corrosion resistance.
Transportation pipeline: used to transport oil and natural gas, pickling can remove surface impurities and extend service life.

2. Chemical industry
Chemical equipment: used to manufacture equipment such as reactors and heat exchangers, pickling can remove oxide scale and rust, ensure surface cleanliness and improve corrosion resistance.
Pipeline system: used to transport corrosive media, pickling can remove surface impurities and extend service life.

3. Automobile manufacturing industry
Automotive parts: used to manufacture exhaust systems, fuel systems and other parts, pickling can remove oxide scale and rust, ensure smooth surface and improve corrosion resistance.
Structural parts: used to manufacture body structural parts, pickling can remove surface impurities and improve coating quality.

4. Machinery manufacturing industry
Hydraulic and pneumatic components: used to manufacture hydraulic cylinders, cylinders and other components. Pickling can remove scale and rust, ensure smooth surface and improve sealing performance.
Transmission parts: used to manufacture shafts, gears and other parts. Pickling can remove surface impurities and improve wear resistance.

5. Construction industry
Structural steel pipes: used for building structure support. Pickling can remove scale and rust, ensure smooth surface and improve corrosion resistance.
Decorative pipes: used for building decoration. Pickling can remove surface impurities and improve aesthetics.

6. Power industry
Boiler tubes: used to manufacture boilers and heat exchangers. Pickling can remove scale and rust, ensure clean surface and improve heat transfer efficiency.
Condenser tubes: used to manufacture condensers. Pickling can remove surface impurities and extend service life.

7. Food and pharmaceutical industry
Sanitary steel pipes: used to transport food and medicines. Pickling can remove scale and rust, ensure clean surface and meet hygiene standards.
Equipment manufacturing: used to manufacture food and pharmaceutical equipment, pickling can remove surface impurities and improve corrosion resistance.

8. Aerospace industry
High-precision pipes: used to manufacture aircraft and spacecraft parts, pickling can remove scale and rust, ensure a smooth surface, improve corrosion resistance and strength.

9. Shipbuilding industry
Marine pipes: used to manufacture ship piping systems, pickling can remove scale and rust, ensure a clean surface, and improve corrosion resistance.
Structural parts: used to manufacture hull structural parts, pickling can remove surface impurities and improve coating quality.

Through the pickling process, metal steel pipe products can achieve higher surface quality and performance in various application fields, meeting the strict requirements of different industries.

Read more: Seamless Steel Pipe Galvanizing Process or Seamless Stainless Steel Pipe Passivation