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What Are the Factors That Affect the Coating of Seamless Steel Pipes?

In order to improve the corrosion resistance of seamless steel pipes and prolong the service life of the products, the seamless steel pipes must be pickled and passivated to form a protective film on the surface.

1. Passivation film of seamless steel pipe

Passivation film belongs to the inhibited metastable structure in thermodynamics, and its maintenance is related to the medium in the environment. But no matter what kind of environment it is used in, the seamless steel pipe must be cleaned regularly to remove the harmful substances attached to the surface.

2. Chloride ions are extremely harmful to the coating of seamless steel pipes

We must strictly control the content of chloride ions in the passivation solution during the passivation of seamless steel pipes. Many chemical materials used for passivation have restrictions on the content of chloride ions. In the configuration of passivation solution water and clean water, there are also strict water quality requirements for chloride ions to ensure that the passivation solution does not contain chloride ions.

3. Low nickel content in seamless steel pipes has low passivation performance

The martensite content and the content of chromium and nickel have a great influence on the passivation performance of the rectangular tube. The more lubricated the surface of the stainless steel, the lower the roughness, the more difficult it is for foreign matter to adhere, and the corrosion will be reduced to the lowest point. Therefore, the surface of the rectangular tube should be finished as much as possible. In addition, the cleaning after passivation must be cautious, so that the remaining acid will promote the anode response, maintain the integrity of the film, and ensure that the appearance of corrosion resistance is strengthened.

4. The surface of seamless steel pipes will inevitably be attached to oil during production and transportation

This will affect the quality of rust removal and phosphating, and reduce the bonding force between the coating and the substrate. This requires the use of organic solvents to dissolve saponified and unsaponified oils to remove oil stains. Commonly used organic solvents include ethanol, gasoline for cleaning, toluene, carbon tetrachloride, trichloroethylene and so on. Among the more effective solvents are carbon tetrachloride and trichloroethylene, which do not burn and can be used for degreasing at higher temperatures.

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