Overview of Pickling of Seamless Steel Pipes

The method of using acid solution to remove scale and rust on the surface of steel is called pickling. Scale, rust and other iron oxides react chemically with acid solution to form salts that dissolve in acid solution and are removed. Acids used for pickling include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and mixed acid.

Common media for pickling of seamless steel pipes and erw tube: sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid. Be sure to add pickling corrosion inhibitors during pickling to prevent acid corrosion of metals.

Pickling process of seamless steel pipes

Mainly include immersion pickling method, spray pickling method and acid paste rust removal method. Generally, immersion pickling method is used, and spraying method can be used in mass production. Steel parts are generally pickled in 10% to 20% (volume) sulfuric acid solution at a temperature of 40°C. When the iron content in the solution exceeds 80g/L and ferrous sulfate exceeds 215g/L, the pickling solution should be replaced.

At room temperature, pickling steel with 20% to 80% (volume) hydrochloric acid solution is not prone to over-corrosion and hydrogen embrittlement. Since acid has a great corrosive effect on metals, corrosion inhibitors need to be added. After cleaning, the metal surface becomes silvery white, and the surface is passivated at the same time, improving the corrosion resistance of stainless steel. In order to eliminate the adsorption on the surface of diatomaceous earth carriers and reduce the tailing of chromatographic peaks, the carrier needs to be pickled or alkaline washed before use. Pickling is to soak the carrier in 6mol/L hydrochloric acid for 2h or heat and soak it in concentrated hydrochloric acid for 30min, filter, wash with water to neutral, and dry. Pickling can remove impurities such as iron, aluminum, calcium, and magnesium on the surface, but cannot remove silanol groups. Pickling carriers are suitable for analyzing acidic samples.

The role of pickling seamless steel pipes

The surface of precision seamless steel pipes is degreased and rusted to prepare for the next process. In the production process, the pickling process is to remove the surface oxide scale, and then after lubrication treatment (carbon steel-phosphorus saponification, stainless steel-tallow lime, copper and aluminum tubes-oiling), use the old process-copper plating), and then draw deep processing. If the steel pipe is not pickled, there may be oxides and oil stains on the surface, and the phosphating liquid core cannot remove them, and the phosphating quality will be reduced.

Precautions for pickling of seamless pipes

The maintenance of seamless steel pipes in the later stage is actually quite important, especially after leaving the factory. The most important step is pickling. Because it is treated with chemical elements, you need to pay attention to your own safety in terms of safety protection. Especially the staff, you need to wear necessary protective equipment, and the same environment should be carefully checked. You can't just care about one point, check it several times to see if the protective sling of the steel pipe is firm. After this series of inspections are correct, you can work.

Pickling, there is no doubt that the raw material is mainly acid, but the acid content should not be too strong, not more than 20%. When operating and cleaning, the staff must first understand the concentration of the acid and the tonnage and area of ​​the steel pipe. Similarly, while understanding these, it is also necessary for the staff to master the cleaning time. Because when cleaning, the cleaning time is determined according to the weight of the steel pipe. It cannot be washed for a long time, and the washing time must be grasped.

In addition, vibration is inevitable during the cleaning process. Especially when the lower pipe enters the acid tank, the steel pipe will inevitably tilt. At this time, special attention should be paid to avoid splashing hydrochloric acid and accidentally injuring people next to you. During the pickling process, unrelated personnel must not approach the pickling project to avoid accidents. After the wastewater is treated, it cannot be discharged into the soil, which will pollute the soil quality.

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