Which process forms a protective oxide layer on stainless steel to improve corrosion resistance?

Which process forms a protective oxide layer on stainless steel to improve corrosion resistance?

• A. Anodizing
• B. Galvanizing
• C. Painting
• D. Passivation

Answer: (D)

Passivation builds a stable, chromium-rich oxide protective film on stainless steel that dramatically boosts corrosion resistance. Stainless steel contains chromium, and when the surface is clean, oxygen from the environment reacts with chromium to form a thin, adherent chromium oxide layer. This passive film acts as a barrier to corrosion and can repair itself if damaged. In practice, a passivation step uses acid cleaners to remove surface iron and other contaminants, ensuring the chromium oxide layer can form uniformly across the surface. This treatment strengthens the natural corrosion resistance of stainless steel, especially in aggressive environments like those with chlorides. Anodizing thickens oxide on other metals, galvanizing adds a zinc coating, and painting applies a protective coating, but none of these specifically enhance the stainless steel’s chromium oxide passive film in the way passivation does.

Passivation builds a stable, chromium-rich oxide protective film on stainless steel that dramatically boosts corrosion resistance. Stainless steel contains chromium, and when the surface is clean, oxygen from the environment reacts with chromium to form a thin, adherent chromium oxide layer. This passive film acts as a barrier to corrosion and can repair itself if damaged. In practice, a passivation step uses acid cleaners to remove surface iron and other contaminants, ensuring the chromium oxide layer can form uniformly across the surface. This treatment strengthens the natural corrosion resistance of stainless steel, especially in aggressive environments like those with chlorides. Anodizing thickens oxide on other metals, galvanizing adds a zinc coating, and painting applies a protective coating, but none of these specifically enhance the stainless steel’s chromium oxide passive film in the way passivation does.