What are the standards and procedures for pickling and passivation of carbon steel pipes

Posted by zora li on March 22nd, 2024

Pickling and passivation of carbon steel pipelines is a common pipeline surface treatment method. Through the pickling and passivation process, the oxides on the surface of the pipeline can be removed, the roughness of the inner wall of the pipeline can be reduced, the corrosion resistance of the pipeline can be increased, and the pipeline can be extended. service life. The following will introduce you to the standards and processes for pickling and passivation of carbon steel pipelines.

The standard is an important basis for ensuring the quality and stability of pickling and passivation, and is applicable to carbon steel pipes for various purposes. Standards usually include the following aspects: preparation and use of pickling solutions, selection and use of passivating agents, concentration and operating time of passivating agents, processing and testing of pipes after pickling and passivation, etc.

The first is the preparation and use of pickling liquid. Pickling liquid is the main agent for pickling and passivation. Dilute hydrochloric acid or sulfuric acid is usually used. Its concentration and temperature need to be adjusted according to the material, size and surface condition of the specific pipeline. Generally speaking, the concentration of pickling liquid for carbon steel pipes is 10-15%, and the temperature is between 40-60 degrees Celsius. During the pickling and passivation process, it is necessary to maintain the stability of the concentration and temperature of the pickling solution, detect it regularly and make timely adjustments.

The second is the selection and use of passivating agents. Passivation agent is a chemical reagent used to form a protective layer, generally including copper subchloride, sodium nitrite, etc. The selection of passivating agent needs to be determined according to the specific requirements of the pipeline and the use environment. Pay attention to the dosage and operating time when using it.

Passivant concentration and operating time are also key points that need to be paid attention to during the pickling and passivation process. Generally speaking, the concentration of passivating agent should be within the appropriate range. Too high or too low will affect the pickling passivation effect. The operating time needs to be adjusted according to the size, material and surface condition of the specific pipeline, generally between 30 minutes and 2 hours.

The processing and testing of pipelines after pickling and passivation are also very important links. After the pickling and passivation is completed, the pipeline needs to be processed to thoroughly clean the residual acid, passivation agent and other substances inside and outside the pipeline. After cleaning is completed, the corrosion resistance of the pipeline needs to be tested. The protective ability of the pipeline can be evaluated through electrochemical testing, salt spray testing and other methods.

To summarize, the standards and processes for pickling and passivating carbon steel pipelines include the preparation and use of pickling solutions, the selection and use of passivating agents, the concentration and operating time of passivating agents, the processing and testing of pipes after pickling and passivation, etc. aspect. Operating in accordance with standards and procedures can effectively improve the corrosion resistance of carbon steel pipelines and extend their service life. When choosing a pickling and passivating service provider, you should choose a company with experience and professional technology to ensure the pickling and passivation effect and quality.