The decisive role of chromium in stainless steel: There is only one element that determines the properties of stainless steel, which is chromium, and each stainless steel contains a certain amount of chromium. To date, there is no stainless steel without chromium.

The fundamental reason why chromium has become the main element that determines the properties of stainless steel is that adding chromium as an alloying element to the steel promotes the internal contradictory movement to the development of the aspect that is conducive to resisting corrosion damage. This change can be explained from the following aspects:

①Cr increases the electrode potential of iron-based solid solution,

②Cr absorbs iron electrons to passivate iron. Passivation is a phenomenon in which the corrosion resistance of metals and alloys is improved due to the blocked anodic reaction. There are many theories of passivation of constituent metals and alloys, mainly including thin film theory, adsorption theory and electron arrangement theory.