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Analysis of the Reasons Why Stainless Steel Butterfly Valves Rust

Stainless steel butterfly valve (also known as stainless steel flap valve) adopts a three-eccentric multilayer metal hard-sealed structure, which is widely used in industrial pipelines such as metallurgy, electric power, petrochemical, water supply and drainage, and municipal construction, where the medium temperature is ≤425℃, for flow regulation and fluid cutoff. This valve uses a three-eccentric structure, and the sealing surfaces of the valve seat and disc are made of different hardness and stainless steel, with good corrosion resistance and long service life.


Advantages of stainless steel butterfly valve


Stainless steel butterfly valve can resist oxidation in the atmosphere, and has corrosion resistance in acidic, alkaline, and salt media. Therefore, the all-stainless steel butterfly valve has characteristics such as wear resistance and corrosion resistance. These characteristics can fully reflect the advantages of stainless steel materials, but in some special environmental media, rusting is still possible.


Stainless steel butterfly valve relies on a layer of extremely thin, strong and dense stable chromium-rich oxide film (protective film) formed on its surface to prevent oxygen atoms from continuing to penetrate and oxidize, and to achieve anti-corrosion ability. Once for some reason, this thin film is continuously damaged, oxygen atoms in the air or liquid will continue to penetrate, or iron atoms in the metal will continuously dissociate, forming loose oxide iron, and the metal surface will be continuously corroded.


Why does stainless steel butterfly valve rust?


  • The surface of the stainless steel butterfly valve is contaminated with organic juice, and under the condition of water and oxygen, organic acids are formed, which will corrode the metal surface over time.

  • The surface of the stainless steel butterfly valve contains dust or foreign metal particles with other metal elements attached to it. In humid air, the attachment and the stainless steel are connected into a micro-battery, triggering an electrochemical reaction and destroying the protective film, which is electrochemical corrosion.

  • The surface of the stainless steel butterfly valve is contaminated with acid, alkali, salt substances (such as alkaline water and lime water splashed on the wall during decoration), causing local corrosion.

  • The stainless steel butterfly valve is exposed to polluted air (such as the atmosphere containing a large amount of sulfides, carbon monoxide, and nitrogen oxides). When it encounters condensation water, it forms sulfuric acid, nitric acid, and acetic acid droplets, causing chemical corrosion. All of the above conditions can cause damage to the protective film on the surface of stainless steel, leading to rusting.


To ensure that stainless steel does not rust, it is recommended to regularly clean and scrub the surface of decorative stainless steel to remove attachments and eliminate external factors that cause rusting. Reasonably choose a suitable operating condition that suits your own use.

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