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Why Do Brown Rust Spots Appear On The Surface Of Stainless Steel Plates?

Jan. 07, 2020

How to deal with brown rust spots on the surface of stainless steel plate. When brown rust spots (spots) appear on the surface of stainless steel plate, people think that stainless steel plate is not rusty, and it may be that the steel has a problem. In fact, this is a one-sided wrong view of lack of understanding of stainless steel plates. Stainless steel plates can also rust under certain conditions.


The stainless steel plate has the ability to resist atmospheric oxidation, that is, stainless steel, and also has the ability to corrode in the medium containing acid, alkali, and salt-that is, corrosion resistance. However, the size of its anti-corrosion ability changes with the chemical composition of the steel itself, the mutual state, the conditions of use, and the type of environmental medium. Such as 304 Stainless Steel Plate, it has absolutely excellent rust resistance in a dry and clean atmosphere, but it will be rusted quickly when it is moved to the seashore area in sea fog containing a large amount of salt; The 316 Stainless Steel Sheet performed well. Therefore, not any kind of stainless steel plate can be corrosion-resistant and rust-proof under any environment.


316 Stainless Steel Sheet


316 Stainless Steel Sheet


The stainless steel plate is a thin, strong and stable chromium-rich oxide film (protective film) formed on its surface, which prevents oxygen atoms from infiltrating and continuing to oxidize, and obtains the ability to resist rust. Once for some reason, the film is constantly destroyed, oxygen atoms in the air or liquid will continue to infiltrate or iron atoms in the metal will be continuously separated out, forming loose iron oxide, and the metal surface will be continuously rusted. There are many forms of damage to this surface film. The following are common in daily life:


1. The surface of the stainless steel plate contains dust or other metal particles containing other metal elements. In humid air, the condensate between the material and the stainless steel plate connects the two into a micro battery, which triggers electricity. Chemical reaction, damage to the protective film is called electrochemical corrosion.

2. Organic matter juices (such as vegetables, noodle soup, sputum, etc.) are adhered to the surface of stainless steel plates. In the presence of water and oxygen, they form organic acids. For a long time, organic acids will corrode the metal surface.

3. The surface of the stainless steel plate contains acids, alkalis, and salts (such as alkali water and lime water splashing from the wall), which may cause local corrosion.

4. In contaminated air (such as an atmosphere containing a large amount of sulfide, carbon oxide, and nitrogen oxide), when it meets condensed water, it forms sulfuric acid, nitric acid, and acetic acid liquid points, causing chemical corrosion.


The above conditions can cause the damage of the protective film on the surface of the stainless steel plate to cause corrosion. Therefore, to ensure that the metal surface is permanently bright and not rusted, we recommend:

1. The surface of the decorative stainless steel plate must be cleaned and scrubbed frequently to remove attachments and eliminate external factors that cause rust.

2. Use 316 stainless steel plate in the seaside area. The 316 material can resist seawater corrosion.

3. On the market, the chemical composition of some stainless steel plates and tubes cannot meet the corresponding national standards and cannot meet the 304 material requirements. Therefore, it will also cause rust, which requires users to carefully choose products from reputable manufacturers.


The above is the reason for the brown rust spots on the surface of the stainless steel plate by 316l Stainless Steel Sheet Manufacturer. I hope it can help everyone.

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