Why stainless steel has corrosion resistance?
All metals and oxygen in the atmosphere in the reaction was carried out to form an oxide film on the surface. Unfortunately, the formation of iron oxide on the plain carbon steel to proceed with the oxidation, so that the corrosion continues to expand, the final pore formation. Paint or oxidation-resistant metal (e.g., zinc, nickel and chromium) electroplating can use to ensure that the surface of carbon steel, however, as people know, this protection is only a thin film. If the protective layer is damaged, the following steel began to rust.
The corrosion resistance of stainless steel depends on chromium, chromium is part of stainless, so the protection methods are different.
Reached 11.7% or more of the added amount of Cr, the steel resistant to atmospheric corrosion significantly increased, but the chromium content is higher, although still improve corrosion resistance, but not obvious. The reason is alloyed with chromium steel, the surface oxide of the type of change has become similar to the pure chromium metal is formed on the surface of the oxide.
This tight adhesion of chromium-rich oxide protective surface, to prevent further oxidation. This very thin oxide layer, through which you can see the natural luster of the surface of the steel, stainless steel with unique surface. Moreover, if damage to the surface, exposing the steel surface and the atmospheric reaction self-repair, and re-formation of such an oxide passivation film, and continue to play a protective role.