Common knowledge of flange pipeline: why stainless steel flange rusts?

Stainless steel flange is deeply loved by people because of its beauty, corrosion resistance and not easy to be damaged. However, when there are brown rust spots on the surface of stainless steel flange, people will be surprised: why does “stainless steel” rust? If it does, is it still “stainless steel”? Is the material unqualified?

In fact, this is a wrong view of stainless steel, because stainless steel will rust under certain conditions.

Stainless steel has the ability of corrosion in the medium containing acid, alkali and salt, that is, corrosion resistance; It also has the ability to resist atmospheric oxidation, that is, rust resistance; However, its corrosion resistance varies with the chemical composition of the steel itself, service conditions and the type of environmental medium. For example, 304 stainless steel has absolutely excellent corrosion resistance in a dry and clean environment, but when it is moved to the coastal area, it will quickly rust in the sea fog containing a lot of salt; 316 material has good performance. Therefore, in any environment, not any kind of stainless steel can not rust.

A thin, firm, fine and stable chromium rich oxide film is formed on the surface of stainless steel, so as to obtain the ability of corrosion resistance. Once for some reason, the film is constantly damaged. Oxygen atoms in the air or liquid will continuously penetrate or iron atoms in the metal will continuously separate out to form loose iron oxide, the metal surface will be continuously rusted, and the stainless steel protective film will be damaged.

 

 Casting Hinge

 

Corrosion of several common stainless steels in daily life

The surface area of stainless steel collects dust, which contains attachments of other metal particles. In humid air, the condensate between the attachment and stainless steel connects them into a micro battery, which leads to power generation chemical reaction and the destruction of the protective film, which is called electron chemical corrosion; The surface of stainless steel adheres to organic juice (such as melons and vegetables, noodle soup, phlegm, etc.), which constitutes organic acid in the case of water and oxygen.

The surface of stainless steel will adhere to substances containing acid, alkali and salt (such as alkali water and lime water splashing on the decoration wall), resulting in local corrosion; In polluted air (such as atmosphere containing a large amount of sulfide, carbon oxide and nitrogen oxide), sulfuric acid, nitric acid and acetic acid will be formed when encountering condensed water, resulting in chemical corrosion.

 Casting pipe fittings

The above conditions may damage the protective film on the surface of stainless steel and cause corrosion. Therefore, in order to ensure that the metal surface is permanently bright and free from corrosion, we suggest that the stainless steel surface must be cleaned and scrubbed to remove attachments and external factors. 316 stainless steel should be used in coastal areas, which can resist seawater corrosion; The chemical composition of some stainless steel pipes in the market can not meet the corresponding national standards, and can not meet the 304 material requirements, which will also cause rust, which requires users to carefully select the products of reputable manufacturers.

Factory from long range

Hebei Junya Precision Machinery Co., Ltd., founded in 2017, is a high-tech enterprise integrating product design, mold development, casting, processing, surface treatment, testing and inspection and sales services. The factory covers an area of 5000 square meters and is located in Huanghua economic and Technological Development Zone, Hebei Province. The company has superior geographical location and convenient transportation. After years of development, the company has introduced advanced production equipment and management experience in various industries, and trained dozens of excellent professional R & D and technical talents.

At present, the company has more than 100 employees and more than 20 technical and R & D personnel. The company’s main products are stainless steel cast pipe fittings, quick connectors, ball valves, check valves, precision accessories, marine hardware, cast auto parts, etc. The product material is mainly 304 304L 316 316L CF8M WCB 1.4408, etc. The company officially passed ISO9000 certification in 2020 and is actively preparing for TS16949 quality system certification. With its good product quality and reputation, the company has become more and more prominent in the international market, with partners all over the world.

In 2019, the export volume accounted for more than 60% of the total sales, and has established long-term and stable cooperative relations with many enterprises in Europe, the United States and Japan. The company always adheres to the business philosophy of heart, innovation and ingenuity. Based on the principle of seeking development from R & D, meeting opportunities in development, building trust in opportunities and consolidating contacts in trust, we look forward to cooperating with you. For details, please contact 18902146189.


Post time: May-20-2022