Corrosion of Stainless Steel: Test Methods and Proper Expectations
Stainless steels – naturally corrosion-resistant metal alloys – are auto-passivating, which means they spontaneously produce a passivation layer (a thin passive film) in oxidizing environments like air or moisture. The passivation layer is non-reactive: it inhibits the electrochemical reactions that would normally take place between the base material and the environment.
Although the passivation layer can be damaged, exposing the material beneath, it will naturally repair itself as long as the base stainless steel material is free of contaminant. Alternatively, an electrochemically-applied coating such as zinc plating is simply a sacrificial layer that will eventually deplete and give way to the material beneath.