What does passivation refer to in metallurgy?

Passivation in metallurgy primarily refers to the process of creating a protective oxide layer on the surface of metals. This layer serves as a barrier that limits further corrosion by preventing the underlying metal from coming into contact with aggressive environments, such as moisture or corrosive chemicals.

The formation of this oxide layer can be spontaneous or can be induced through chemical treatment, and it significantly enhances the material's resistance to corrosion. For example, stainless steels are known for their ability to form a passive oxide layer, which is crucial for their corrosion resistance. This characteristic is particularly important in applications where materials are exposed to harsh conditions.

Other options, while relevant to materials processing, do not accurately represent the concept of passivation. Adding heat, removing impurities, or changing the mechanical structure may contribute to different processes in metallurgy but do not specifically define passivation.