There are four types of carbon steel commonly used in the hollow metal doors and frames industry:
- Cold rolled steel: Not corrosion resistant. Must be protected with a rust inhibitive primer.
- Galvanized steel: Cold rolled steel protected with a zinc coating, for corrosion resistance, (G designation). Must be covered with a special primer before painting.
- Galvannealed steel: Heat treated hot dipped galvanized steel with a zinc-iron alloy coating, (A designation). Suitable for immediate painting after normal cleaning.
- Stainless steel: Contains more chromium and nickel which offer high corrosion resistance.