Why does stainless steel also rust?
Why does stainless steel also rust? When brown rust spots (spots) appear on the surface of stainless steel pipes, people are greatly surprised: they believe that "stainless steel does not rust, rust is not stainless steel, it may be a problem with the steel quality". In fact, this is a one-sided misconception about a lack of understanding of stainless steel. Stainless steel can also rust under certain conditions.
Stainless steel has the ability to resist atmospheric oxidation - i.e. rust resistance - and also has the ability to resist corrosion in media containing acids, alkalis, and salts - i.e. corrosion resistance. However, its corrosion resistance varies depending on the chemical composition, additive state, service conditions, and type of environmental medium of the steel itself. For example, 304 steel pipes have absolutely excellent rust resistance in a dry and clean atmosphere, but when moved to coastal areas, they quickly rust in sea mist containing a large amount of salt; However, 316 steel pipes performed well. Therefore, not any type of stainless steel can withstand corrosion and rust in any environment.
Stainless steel is a stable chromium rich oxide film (protective film) formed on its surface, which is extremely thin, sturdy, and fine, preventing the continued infiltration and oxidation of oxygen atoms, thus obtaining the ability to resist corrosion. Once for some reason, this thin film is constantly damaged, oxygen atoms in air or liquid will continuously penetrate or iron atoms in metal will continuously separate, forming loose iron oxide, and the metal surface will also be constantly corroded. This kind of surface facial mask is damaged in many ways, and the following types are common in daily life:
1. Dust containing other metal elements or attachments of dissimilar metal particles accumulate on the surface of stainless steel. In humid air, the condensate between the attachments and the stainless steel forms a micro battery, triggering an electrochemical reaction and damaging the protective film, which is called electrochemical corrosion.
2. Organic juices (such as melons, noodles, phlegm, etc.) adhere to the surface of stainless steel, forming organic acids in the presence of water and oxygen. Over time, organic acids corrode the metal surface.
3. The surface of stainless steel adheres to substances containing acids, alkalis, and salts (such as alkaline water and lime water splashing during wall decoration), causing local corrosion.
4. In polluted air (such as atmospheres containing large amounts of sulfides, carbon oxides, and nitrogen oxides), when encountering condensed water, sulfuric acid, nitric acid, and acetic acid droplets form, causing chemical corrosion.
The above situations can cause damage to the protective film on the surface of stainless steel, leading to corrosion. So, to ensure that the metal surface is permanently bright and not corroded, we recommend:
1. It is necessary to regularly clean and scrub the surface of decorative stainless steel to remove attachments and eliminate external factors that cause modification.
2. In coastal areas, 316 stainless steel should be used, which can resist seawater corrosion. 3. Some stainless steel pipes in the market cannot meet the corresponding national standards for chemical composition and cannot meet the requirements of 304 material. Therefore, it can also cause rusting, which requires users to carefully choose products from reputable manufacturers.
Stainless steel has the ability to resist atmospheric oxidation - i.e. rust resistance - and also has the ability to resist corrosion in media containing acids, alkalis, and salts - i.e. corrosion resistance. However, its corrosion resistance varies depending on the chemical composition, additive state, service conditions, and type of environmental medium of the steel itself. For example, 304 steel pipes have absolutely excellent rust resistance in a dry and clean atmosphere, but when moved to coastal areas, they quickly rust in sea mist containing a large amount of salt; However, 316 steel pipes performed well. Therefore, not any type of stainless steel can withstand corrosion and rust in any environment.
Stainless steel is a stable chromium rich oxide film (protective film) formed on its surface, which is extremely thin, sturdy, and fine, preventing the continued infiltration and oxidation of oxygen atoms, thus obtaining the ability to resist corrosion. Once for some reason, this thin film is constantly damaged, oxygen atoms in air or liquid will continuously penetrate or iron atoms in metal will continuously separate, forming loose iron oxide, and the metal surface will also be constantly corroded. This kind of surface facial mask is damaged in many ways, and the following types are common in daily life:
1. Dust containing other metal elements or attachments of dissimilar metal particles accumulate on the surface of stainless steel. In humid air, the condensate between the attachments and the stainless steel forms a micro battery, triggering an electrochemical reaction and damaging the protective film, which is called electrochemical corrosion.
2. Organic juices (such as melons, noodles, phlegm, etc.) adhere to the surface of stainless steel, forming organic acids in the presence of water and oxygen. Over time, organic acids corrode the metal surface.
3. The surface of stainless steel adheres to substances containing acids, alkalis, and salts (such as alkaline water and lime water splashing during wall decoration), causing local corrosion.
4. In polluted air (such as atmospheres containing large amounts of sulfides, carbon oxides, and nitrogen oxides), when encountering condensed water, sulfuric acid, nitric acid, and acetic acid droplets form, causing chemical corrosion.
The above situations can cause damage to the protective film on the surface of stainless steel, leading to corrosion. So, to ensure that the metal surface is permanently bright and not corroded, we recommend:
1. It is necessary to regularly clean and scrub the surface of decorative stainless steel to remove attachments and eliminate external factors that cause modification.
2. In coastal areas, 316 stainless steel should be used, which can resist seawater corrosion. 3. Some stainless steel pipes in the market cannot meet the corresponding national standards for chemical composition and cannot meet the requirements of 304 material. Therefore, it can also cause rusting, which requires users to carefully choose products from reputable manufacturers.
