Why Should Seamless Steel Pipes be Pickled?

  • The method of using an acid solution to remove oxide scale and rust on the surface of the steel is called pickling. Iron oxides such as scale and rust react chemically with the acid solution to form salts which are dissolved in the acid solution and removed. Acids for pickling include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and mixed acids.

    The dipping and pickling method is generally used, and the spray method can be used in mass production. Steel parts are generally pickled in a 10%-20% 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. At room temperature, the steel is pickled with 20%-80% hydrochloric acid solution to prevent corrosion and hydrogen embrittlement.

    Since acid has a great corrosion effect on metals, corrosion inhibitors should be added. After cleaning, the metal surface becomes silvery white, and the surface is passivated to improve the corrosion resistance of stainless steel. In order to eliminate the surface adsorption of the diatomaceous earth carrier and reduce the tailing of the chromatographic peak, the carrier needs to be acid washed or alkaline washed before use. Pickling is to soak the carrier with 6mol/L hydrochloric acid for 2 hours or heat and soak with concentrated hydrochloric acid for 30 minutes, filter, wash with water to neutrality, and dry. Pickling can remove iron, aluminum, calcium, and other impurities on the surface, but cannot remove silanol groups. The pickling carrier is suitable for the analysis of acidic samples.

    Degrease and rust the surface of precision seamless steel pipes, and prepare for the next process. In the production process, the pickling process is to remove the surface oxide scale, after which it undergoes lubrication treatment, and then undergoes deep drawing processing. If the steel pipe is not pickled, there may be oxides and oil stains on the surface, and the nuclear energy of the phosphating solution cannot remove them, and the quality of phosphating will be reduced.

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