Why does stainless steel also rust?
Stainless steel has the ability to resist atmospheric oxidation - that is, rust resistance, and also has the ability to corrode in media containing acids, alkalis and salts - that is, corrosion resistance.
However, the size of its anti-corrosion ability varies with the chemical composition of its steel itself, the state of mutual addition, the conditions of use and the type of environmental media.
For example, 304 steel pipe has absolutely excellent anti-corrosion ability in a dry and clean atmosphere, but if it is moved to a seaside area, it will rust soon in the sea fog containing a lot of salt; and 316 steel pipe shows good.
Therefore, it is not any kind of stainless steel that can resist corrosion and rust in any environment.
The surface film is damaged in the following forms:
On the surface of stainless steel, dust containing other metal elements or attachments of dissimilar metal particles accumulate. In humid air, the condensed water between the attachments and the stainless steel connects the two into a micro-battery, which triggers an electrochemical reaction. , the protective film is damaged, called electrochemical corrosion.
The surface of stainless steel adheres to organic juice. In the presence of water and oxygen, organic acid is formed. For a long time, organic acid will corrode the metal surface.
The surface of stainless steel adheres to substances containing acids, alkalis and salts (such as alkali water and lime water splashing from the decoration walls), causing local corrosion.
In the polluted air (such as the atmosphere containing a large amount of sulfide, carbon oxide and nitrogen oxide), when encountering condensed water, it will form liquid spots of sulfuric acid, nitric acid and acetic acid, causing chemical corrosion.
To ensure that the metal surface is permanently bright and not rusted, it is recommended to:
1. The surface of decorative stainless steel must be cleaned and scrubbed frequently to remove attachments and eliminate external factors that cause modification
2. 316 stainless steel should be used in seaside areas, which can resist seawater corrosion.
3. The chemical composition of some stainless steel pipes on the market 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.
