What is the main function of chromium in stainless steel?

What is the main function of chromium in stainless steel?

• A. Corrosion resistance
• B. Hardness
• C. Electrical conductivity
• D. Ductility

Answer: (A)

The main function of chromium in stainless steel is to create a protective, self-healing oxide layer that stops corrosion. When chromium content is sufficient (about 10.5% or more), it forms a thin, dense chromium oxide film on the surface. This passive film acts as a barrier to oxygen and other aggressive species, preventing the iron from oxidizing and rusting. If the surface is scratched, chromium near the surface quickly oxidizes again, reforming the protective layer and preserving corrosion resistance. This passivation is what makes stainless steel resistant to many forms of corrosion, including in oxidizing environments and chlorides, compared with ordinary steel. Other properties like hardness, electrical conductivity, or ductility are influenced by other alloying elements, but chromium's defining role in stainless steel is corrosion resistance.

The main function of chromium in stainless steel is to create a protective, self-healing oxide layer that stops corrosion. When chromium content is sufficient (about 10.5% or more), it forms a thin, dense chromium oxide film on the surface. This passive film acts as a barrier to oxygen and other aggressive species, preventing the iron from oxidizing and rusting. If the surface is scratched, chromium near the surface quickly oxidizes again, reforming the protective layer and preserving corrosion resistance. This passivation is what makes stainless steel resistant to many forms of corrosion, including in oxidizing environments and chlorides, compared with ordinary steel. Other properties like hardness, electrical conductivity, or ductility are influenced by other alloying elements, but chromium's defining role in stainless steel is corrosion resistance.