Which element makes stainless steel rust resistant?

• A. Chromium
• B. Iron
• C. Nickel
• D. Manganese

Answer: (A)

Chromium forms the protective shield that makes stainless steel resistant to rust. When chromium is present, it creates a thin, adherent layer of chromium oxide on the surface in the presence of oxygen. This passive film blocks iron from oxidizing, so water and air can’t corrode the metal. If the surface is scratched, chromium quickly reforms the protective layer, keeping corrosion at bay. Iron alone would rust, which is why stainless steel relies on chromium for its rust resistance. Nickel and manganese contribute to other properties of the alloy, but they don’t establish the self-healing oxide film that chromium provides.