The narrow sense of stainless steel is not easy to rust in the atmosphere, the broad sense of stainless steel refers to the acid, alkali, salt corrosion-resistant steel under specific conditions. The results show that the corrosion resistance of steel increases with the increase of chromium content in weak medium such as atmosphere, water and nitric acid. When the chromium content is more than 10%, the corrosion resistance of steel changes abruptly, from easy to not easy to rust, from non-corrosion to corrosion resistance. Therefore, stainless steel is usually referred to as an iron-based alloy with a chromium content of more than 12%. Stainless steel is widely used in petrochemical industry, atomic energy, light industry, textile, food and household appliances because of its excellent corrosion resistance, formability, compatibility and toughness in a wide range of temperatures.
GBT20878 defines: stainless steel, corrosion resistance as the main characteristics, and the chromium content is at least 10.5%, carbon content is not more than 1.2%.