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Alloy 20, also known as Carpenter 20, is a nickel-iron-chromium stainless steel alloy designed for exceptional corrosion resistance, particularly in sulfuric acid environments. It is widely used in chemical processing, pharmaceutical, and marine industries where superior resistance to acids, pitting, and stress corrosion cracking is required.

Properties

Properties

  • Superior Corrosion Resistance – Excellent resistance to sulfuric acid, chlorides, phosphoric acid, and nitric acid.
  • High Nickel Content (~32-38%) – Provides enhanced stress corrosion cracking (SCC) resistance.
  • Excellent Pitting & Crevice Corrosion Resistance – Ideal for aggressive chemical and marine environments.
  • Moderate Strength & Ductility – Offers good mechanical properties with easy fabrication and welding.
  • Resists Intergranular Corrosion – Due to stabilization with niobium (Nb), preventing sensitization.

Alloy 20 vs. Other Valve Materials
• Better sulfuric acid resistance than 316SS and 317SS
• More corrosion-resistant than duplex stainless steels but not as strong mechanically
• More cost-effective than Hastelloy® in some chemical applications

Limitations

Limitations

  • Higher Cost Than Stainless Steel – More expensive due to high nickel and chromium content.
  • Not as Strong as Duplex or Super Duplex Steels – May not be ideal for high-pressure applications requiring extreme mechanical strength.
  • Limited High-Temperature Performance – Can degrade at temperatures above 537°C (1000°F).

Common Applications

Common Applications

Chemical Processing Valves – Used in sulfuric acid, nitric acid, phosphoric acid, and chloride-rich environments.
Food & Pharmaceutical Valves – FDA-compliant for sanitary and high-purity applications.
Marine & Offshore Valves – Resists saltwater and brine corrosion better than 316SS.
Pulp & Paper Industry Valves – Handles bleaching agents and acidic process fluids.
Power Plant & Heat Exchanger Valves – Used in high-temperature acidic environments.