Although stainless steel has strong corrosion resistance, it will still rust under certain conditions. In order to enhance its corrosion resistance, especially after welding, turning, stamping and other processing treatments, stainless steel needs to be passivated.
Passivation is a rust and corrosion prevention process that improves the crystal structure and surface roughness of stainless steel materials that have been altered by processing, thereby reducing their rust resistance. The basic principle of passivation can be explained by the thin film theory, that is, the metal surface to generate a very thin, dense and good coverage properties of the passivation film. This film can be firmly attached to the metal surface, effectively isolating the metal and corrosive media, to prevent them from direct contact.
Stainless steel in the process may produce black or yellow oxidized skin, in order to improve its appearance and corrosion resistance, stainless steel after processing must be passivation treatment. This treatment can remove the oxidized skin produced by welding or high temperature processing, so that the surface of stainless steel to restore the luster, and the formation of a layer of chromium-based oxide film, to prevent the secondary oxygen corrosion, so as to achieve the purpose of passivation, to enhance the surface of stainless steel products corrosion-resistant quality performance.
The specific process of stainless steel passivation treatment is as follows:
- Degreasing and degreasing: ensure that the surface of the workpiece is free of oil and dirt.
- activation: immersion 2-5 minutes, if the surface of the workpiece without rust or welding spots and other impurities, you can omit this step.
- passivation: mandatory process, soak for 30 minutes, the longer the time, the more complete the passivation film.
- Neutralization: Soak for 3 minutes, suitable for workpieces with simple surface shape, no gong lines, no blind holes.
- passivation: must go through the process, the time is 3 minutes.
- drying: complete passivation treatment.
Stainless steel pipe pickling passivation
Stainless steel passivation solution is suitable for the treatment of different types of stainless steel workpiece, can not destroy the original color of the workpiece, does not change the size of the workpiece under the premise of significantly improving the salt spray resistance of stainless steel. The process is simple, usually applicable to 200 and 300 series stainless steel, especially suitable for large batches, large production and convenient soaking of small and medium-sized stainless steel workpieces, such as communication equipment components, small furniture components, food machinery accessories, digital electrical components, hardware parts, and so on. Passivated stainless steel parts can pass standard neutral salt spray tests for 48 to 1000 hours, depending on the type of material.
This article is edited by China Steel Pipe.