What is the primary effect of chromium when added to steels?

• A. Hardening agent and tends to increase strength
• B. Basic ingredients in stainless steel
• C. Increases corrosion resistance and oxidation resistance of steels
• D. Little loss of strength at temps up to 482 C - good choice where there is high operating temperatures

Answer: (C)

Chromium’s main effect in steels is to create a protective, self-repairing oxide layer on the surface, which dramatically boosts corrosion and oxidation resistance. When chromium is present at sufficient levels (as in stainless steels), it forms a stable chromium oxide film that adheres to the metal and prevents further rusting and oxygen attack, continually reforming if damaged. This is why chromium most notably strengthens a steel’s resistance to corrosion and high-temperature oxidation, making that option the best description of its primary effect. While chromium can influence hardness or strength in some alloys, those aspects are not the defining impact in steels like stainless grades.