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Why do stainless steel flanges sometimes rust?

2022-05-24

The stainless steel flange is a very thin, firm and fine stable chromium-rich oxide film (protective film) formed on its surface to prevent the continuous infiltration and oxidation of oxygen atoms, and obtain the ability to resist rust. Once the film is damaged continuously for some reason, the oxygen atoms in the air or liquid will continue to infiltrate or the iron atoms in the metal will continue to separate out, forming loose iron oxide, and the metal surface will be continuously corroded.
1. On the surface of the stainless steel flange, there are deposits of dust or heterogeneous metal particles containing other metal elements. In the humid air, the condensed water between the attachment and the stainless steel connects the two into a micro-battery, which causes electricity. The chemical reaction destroys the protective film, which is called electrochemical corrosion.
2. Organic juices (such as vegetables, noodle soup, sputum, etc.) adhere to the surface of the stainless steel flange. In the presence of water and oxygen, organic acids are formed, and organic acids will corrode the metal surface for a long time.
3. The surface of the stainless steel flange contains acid, alkali and salt substances (such as alkali water and lime water splashing on the decoration wall), which causes local corrosion.

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The connection method of the national standard flange!

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2022-05-24