Glossary

Chromium is a hard, lustrous metallic element (chemical symbol Cr, atomic number 24) known for its exceptional corrosion resistance, hardness, and shiny, silvery appearance. It is one of the key alloying elements in many steels—especially stainless steel and chromoly (chromium-molybdenum) alloys—and plays a vital role in improving strength, surface durability, and oxidation resistance.

In metallurgy, chromium serves several important functions:

Corrosion and Oxidation Resistance:
When chromium is added to steel (usually at least 10.5%), it reacts with oxygen in the air to form a thin, stable layer of chromium oxide (Cr₂O₃). This invisible film protects the underlying metal from rusting, which is why stainless steel doesn’t corrode easily.

Hardness and Wear Resistance:
Chromium increases a metal’s surface hardness and resistance to abrasion. This makes it useful for tool steels, bearings, and fasteners that experience friction, impact, or wear.

High-Temperature Strength:
Chromium helps metals maintain their strength and oxidation resistance at elevated temperatures—important for exhaust systems, turbines, and high-heat industrial equipment.

Aesthetic and Protective Coatings:
Chrome plating (electroplating a thin layer of chromium onto another metal) gives parts a mirror-like finish while improving wear and corrosion resistance. This is common on decorative hardware, automotive trim, and tools.

In its pure form, chromium is steel-gray, brittle, and highly polished. Industrially, it’s produced from chromite ore (FeCr₂O₄) and is used not only in metal alloys but also in pigments, refractory materials, and catalysts.