Corrosion resistance
Stainless steels — Properties. Corrosion resistance

The phenomenon of passivity is extremely important, as it forms the basis of the corrosion resistance mechanism of stainless steels. The phenomenon of passivity is characterized by the presence of a very thin film (thickness of the order of 10 to 20 nm), known as a passive film or passive layer, on the surface of the metal alloy, making its corrosion rate negligible. The passive film, which is firmly attached to the metal substrate, prevents or minimizes contact between the alloy and more or less aggressive agents in the surrounding environment.

For the passivity phenomenon to be established and maintained, the iron-chromium alloy must have a minimum chromium content of around 11%. In other words, there is a threshold effect above which passivity...