Several situations of stainless steel rusting and prevention methods

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Shandong Bojing Chemical Machinery discovered during production that stainless steel can also rust under certain conditions. Stainless steel has the ability to resist oxidation in the atmosphere – that is, its rust resistance – as well as the ability to resist corrosion in media containing acids, alkalis, and salts – that is, its corrosion resistance. However, its corrosion resistance varies depending on the chemical composition of the steel itself, its microstructure, operating conditions, and the type of environmental medium. For example, 304 steel pipes have excellent corrosion resistance in a dry and clean atmosphere, but when placed in coastal areas exposed to sea fog containing high levels of salt, they rust very quickly ； The 316 steel pipe, on the other hand, performed well. Therefore, not all stainless steels are resistant to corrosion and do not rust in any environment. Stainless steel gains its rust-resistant properties thanks to an extremely thin, strong, dense, and stable chromium-rich oxide film (protective layer) that forms on its surface, preventing further penetration of oxygen atoms and subsequent oxidation. Once, for some reason, this film is continuously damaged, oxygen atoms from the air or liquid will keep penetrating in, or iron atoms from the metal will continue to separate, forming loose iron oxide; as a result, the metal surface suffers from continuous rusting. There are many ways in which this protective film can be damaged; the most common ones in daily life are as follows: 1. Dust or particles of other metal elements accumulate on the surface of stainless steel. In humid air, the condensation water between these deposits and the stainless steel forms a microcell, triggering an electrochemical reaction that damages the protective film – this phenomenon is known as electrochemical corrosion. 2. Organic substances such as juices from fruits and vegetables, noodle soup, sputum, etc., adhere to the stainless steel surface. In the presence of water and oxygen, these substances form organic acids, which over time cause corrosion of the metal surface. 3. The surface of stainless steel can become adhered to substances containing acids, alkalis, and salts (such as alkaline solutions or lime water used in wall decoration), leading to localized corrosion. 4. In polluted air (such as air containing large amounts of sulfides, carbon monoxide, and nitrogen oxides), when it comes into contact with condensed water, sulfuric acid, nitric acid, and acetic acid are formed, leading to chemical corrosion. All of the above situations can damage the protective film on the surface of stainless steel, leading to rusting. Therefore, to ensure that metal surfaces remain bright permanently and are free from rust, Shandong Bojing Chemical Machinery has identified several prevention methods in its production process: 1. It is necessary to regularly clean and scrub the surface of decorative stainless steel to remove any adhering substances and eliminate external factors that could cause damage. 2. Stainless steel of grade 316 should be used in coastal areas, as this grade can resist corrosion caused by seawater. 3. Some stainless steel pipes available on the market do not meet the corresponding **standards in terms of their chemical composition, and thus do not fulfill the requirements of 304 material. This can also lead to rusting, which requires users to carefully choose products from reputable manufacturers.