Hexavalent chromium is added to steel primarily for which property?

• A. Anticorrosive properties
• B. Electrical conductivity
• C. Magnesium addition
• D. Thermal expansion

Answer: (A)

Hexavalent chromium is added to steel mainly to create a protective, passive surface layer that blocks corrosion. When chromium is present on the surface, it forms a stable chromium oxide film that greatly resists rust and can heal itself if scratched, so the underlying steel stays protected. While chromium coatings can also increase hardness and wear resistance, their primary benefit in steel is anticorrosive. The other options don’t address the primary effect: electrical conductivity isn’t improved by this coating, magnesium addition isn’t the purpose here, and thermal expansion isn’t the main outcome sought.