The corrosion resistance of stainless steel decreases with the increase of carbon content. Therefore, the carbon content of most stainless steels is low, and the maximum carbon content does not exceed 1.2%. The ωc (carbon content) of some steels is even lower than 0.03% (such as 00Cr 12).
The main alloying element in stainless steel is chromium. Only when Cr content reaches a certain value can steel have corrosion resistance. Therefore, the Cr content of stainless steel is at least 10.5%. Stainless steel also contains elements such as nickel, titanium, manganese, nitrogen, niobium, molybdenum, silicon and copper.
Extended data
In the manufacturing process of stainless steel equipment, there will be performance damage, defects and some substances that affect the surface, such as dust, floating iron powder or embedded iron, thermal tempering color and other oxide layers, rust spots, grinding burrs, welding arc initiation marks, welding spatter, flux, welding defects, grease, residual adhesive and paint, chalk and marker marks. Most of them are ignored because of their harmfulness, so they don't pay attention to it and don't do it well.
Once the protective film is damaged, thinned or changed in other ways, the underlying stainless steel will begin to corrode. Corrosion is generally not all over the surface, but at or around the defect. This kind of local corrosion is usually pitting corrosion or crevice corrosion, and these two kinds of corrosion will develop to depth and breadth, but most surfaces are not corroded.
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