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Stainless steel bolts and nuts also rust?
When brown rust spots appear on the surface of stainless steel bolts and nuts, many people will be greatly surprised that "stainless steel can also rust?" In fact, this is a one-sided and wrong view of the lack of certain understanding of stainless steel. Stainless steel is under certain conditions. Stainless steel has a layer of chromium oxide film formed on its surface, which can prevent the penetration and oxidation of oxygen atoms, thus obtaining the ability to resist corrosion. Once this protective film is constantly damaged for some reason, oxygen atoms in air or liquid or iron atoms in metal are constantly separated, forming loose iron oxide, and the surface of stainless steel will be constantly corroded.
The corrosion resistance of stainless steel is changed by its chemical composition, additive state, use environment and environmental media type. Fasteners made of different stainless steel materials have different applicable environments.
Applicable environment of several stainless steel fasteners (conventional environment, marine environment, acid and alkali environment)
304 material fastener
There is no problem when it is used in the environment where there is no contact with liquid in general air
316 material fastener
There is no problem when it is used in general contact with water, common seawater and sewage environment
316L material fastener
It is no problem to use in sewage environment with certain acidity and marine environment
Fastener made of 2205 material
There is no problem when it is used in acidic environment such as phosphoric acid and chloride
904L material fastener
There is no problem when chloride, 70 ℃ seawater, sulfur and acid solution are touched