Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam, and water, and chemically corrosive media such as acids, alkalis, and salts. In fact, stainless steel will rust under certain conditions. The corrosion resistance of stainless steel will be determined by the chemical composition of the steel itself, the conditions of use and the environmental medium.
In our lives, the most commonly used stainless steels are martensitic stainless steel (knives), 201 stainless steel, and the austenitic stainless steel 1Cr18Ni9 whicn is commonly used in the special equipment industry.
Since stainless steel is resistant to corrosion, why is it "rust"?
That's because stainless steel is afraid of "salt", that is, "chloride ions" in salt. Chloride ions will have a tendency to corrode in an environment with water, and in severe cases will cause cracking. Therefore, we will see "rusted" stainless steel knives and stainless steel cups. At the same time, stainless steel will be found to have stress corrosion cracks during inspection.