The method of using acid solution to remove scale and rust on the surface of seamless steel pipes is called seamless pipe pickling, which is a method of cleaning the surface of steel pipes.
The principle of pickling for seamless pipes
Iron oxides (Fe3O4, Fe2O3, FeO, etc.) such as scale and rust react chemically with the acid solution to form salts that are dissolved in the acid solution and removed.
Commonly used acids for pickling of seamless pipes
(1) Pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid and mixed acids. The most commonly used are sulfuric and hydrochloric acids.
(2) The pickling process mainly includes immersion pickling, spray pickling and acid paste rust removal. Generally, immersion pickling is used, and spraying method can be used in mass production.
(3) The industrial concentrated sulfuric acid sold on the market usually contains H2SO475%~97% (mass fraction), and brown industrial sulfuric acid solution can also be used, which contains H2SO475%~78% (mass fraction).
Precautions for pickling of seamless pipes
(1) Seamless pipes are generally pickled in 10%~20% (volume) sulfuric acid solution at a temperature of 40°C. When the iron content in the solution exceeds 80g/L and the ferrous sulfate exceeds 215g/L, the pickling solution should be replaced. Under normal temperature, pickling steel with 20%~80% (volume) hydrochloric acid solution is not prone to over-corrosion and hydrogen embrittlement. Because acid has a strong corrosion effect on metals, it is necessary to add corrosion inhibitors. After cleaning, the metal surface becomes silvery white, and the surface is passivated at the same time, improving the corrosion resistance of seamless pipes. The process of removing scale and adhering salts on the surface of seamless steel pipes with a sulfuric acid solution with a concentration of 5% to 20% is called sulfuric acid pickling.
(2) In order to eliminate the surface adsorption of diatomite carrier and reduce the tailing of chromatographic peaks, the carrier needs to be acid-washed or alkali-washed before use. Pickling is to soak the carrier with 6mol/L hydrochloric acid for 2h or concentrated hydrochloric acid for 30min, filter, wash with water until neutral, and dry. Pickling can remove iron, aluminum, calcium, magnesium and other impurities on the surface, but cannot remove silanol groups. Acid-washed carrier is suitable for analysis of acidic samples
Through pickling, the seamless pipe can achieve better surface quality and corrosion resistance. In the specific production process, the parameters and equipment selection of each process step need to be adjusted and optimized according to the actual situation to ensure the stability and efficiency of the process.
The principle of pickling for seamless pipes
Iron oxides (Fe3O4, Fe2O3, FeO, etc.) such as scale and rust react chemically with the acid solution to form salts that are dissolved in the acid solution and removed.
Commonly used acids for pickling of seamless pipes
(1) Pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid and mixed acids. The most commonly used are sulfuric and hydrochloric acids.
(2) The pickling process mainly includes immersion pickling, spray pickling and acid paste rust removal. Generally, immersion pickling is used, and spraying method can be used in mass production.
(3) The industrial concentrated sulfuric acid sold on the market usually contains H2SO475%~97% (mass fraction), and brown industrial sulfuric acid solution can also be used, which contains H2SO475%~78% (mass fraction).
Precautions for pickling of seamless pipes
(1) Seamless pipes are generally pickled in 10%~20% (volume) sulfuric acid solution at a temperature of 40°C. When the iron content in the solution exceeds 80g/L and the ferrous sulfate exceeds 215g/L, the pickling solution should be replaced. Under normal temperature, pickling steel with 20%~80% (volume) hydrochloric acid solution is not prone to over-corrosion and hydrogen embrittlement. Because acid has a strong corrosion effect on metals, it is necessary to add corrosion inhibitors. After cleaning, the metal surface becomes silvery white, and the surface is passivated at the same time, improving the corrosion resistance of seamless pipes. The process of removing scale and adhering salts on the surface of seamless steel pipes with a sulfuric acid solution with a concentration of 5% to 20% is called sulfuric acid pickling.
(2) In order to eliminate the surface adsorption of diatomite carrier and reduce the tailing of chromatographic peaks, the carrier needs to be acid-washed or alkali-washed before use. Pickling is to soak the carrier with 6mol/L hydrochloric acid for 2h or concentrated hydrochloric acid for 30min, filter, wash with water until neutral, and dry. Pickling can remove iron, aluminum, calcium, magnesium and other impurities on the surface, but cannot remove silanol groups. Acid-washed carrier is suitable for analysis of acidic samples
Through pickling, the seamless pipe can achieve better surface quality and corrosion resistance. In the specific production process, the parameters and equipment selection of each process step need to be adjusted and optimized according to the actual situation to ensure the stability and efficiency of the process.
