Reasons for corrosion of oxide film on the surface of stainless steel pipes

Reasons for corrosion of oxide film on the surface of stainless steel pipes


Sometimes there are brown rust spots on the surface of stainless steel pipes, and many people believe that stainless steel does not rust. Since it rusts, it is definitely a counterfeit product, and this “stainless steel” should be fake. In fact, this understanding is very one-sided and incorrect. Stainless steel can also rust under certain conditions.

Most of the time, stainless steel does not rust because it is protected by an extremely thin and dense stable oxide film on the surface, which can prevent the continuous infiltration and oxidation of oxygen atoms. This is why stainless steel can resist rust. But in some cases, if this thin film is constantly damaged, oxygen atoms in the air or liquid will continuously infiltrate or iron atoms in stainless steel will continuously separate, generating loose iron oxide, and the surface of stainless steel will continuously rust

There are many ways to damage the protective film on the surface of stainless steel, and the following will discuss these corrosion causes.

Surface contamination caused by chemical corrosion

The pollutants such as oil, dust, acid, alkali, and salt attached to the surface of stainless steel can be transformed into corrosive media under certain conditions, which will react chemically with some components in the stainless steel substrate, forming chemical corrosion and ultimately rusting.

Carbon steel pollution caused by electrochemical corrosion

The scratches formed by the contact between stainless steel and carbon steel will form an electrochemical corrosion with the corrosive medium, forming a primary battery. In addition, the attachment of rust prone substances such as cutting slag and splashes generated by cutting and the formation of corrosive media form the primary battery, resulting in electrochemical corrosion.

Usually, as long as the protective film on the surface of stainless steel is not damaged, cracked, or contaminated, stainless steel will not rust.

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Post time: May-22-2024