The factors that affect the passivation coating of seamless steel pipes
mainly include the following four points: The passive film of seamless steel pipes is a suppressed 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, it must be regularly cleaned to remove harmful substances attached to the surface.
Chloride ions are extremely harmful to the passivation coating
of seamless steel pipes. We must strictly control the content of chloride ions in the passivation solution during the process of stopping the passivation of the external surface. Many chemical materials for passivation have limited requirements for chloride ions. In the configuration of passivation liquid and cleaning water, there are also strict water quality requirements for chloride ions to ensure that the passivation waste does not contain chloride ions.
The low nickel content in seamless steel pipes has low passivation performance, so 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. In addition, the cleaning after passivation should be stopped carefully, so that the remaining acid can promote the anode response, maintain the integrity of the film, and ensure that the appearance of corrosion resistance is strengthened.
In the production and transportation of seamless steel pipes, oil stains will inevitably adhere to the surface, which will affect the quality of rust removal and phosphating, and reduce the adhesion between the coating and the substrate. Mainly use 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, etc. Among the more effective solvents are carbon tetrachloride and trichloroethylene, which will not burn and can be used for degreasing at higher temperatures.
Tips: ASTM A53/SA53 seamless and welded steel pipe is a general, all-purpose pipe used in generator plants, refineries, compressor stations, natural gas transmission, and steam conduction.