ASTM B622 ALLOY C22 Nickel Alloy Steel Heat Exchanger Tube , Air Cooler

ASTM B622 is a standard specification for seamless nickel and nickel alloy pipes and tubes designed for corrosive service environments. Alloy C22 (UNS N06022), commonly known as Hastelloy C-22, is a nickel-chromium-molybdenum-tungsten alloy renowned for exceptional corrosion resistance. It is specifically engineered for heat exchangers operating in aggressive chemical and high-temperature environments.

Material Composition:
Alloy C22’s composition is optimized for performance in oxidizing and reducing media:

• Nickel (Ni): ~56% (base element for ductility and corrosion resistance).

• Chromium (Cr): 20–22.5% (enhances oxidation resistance).

• Molybdenum (Mo): 12.5–14.5% (resists reducing acids and pitting).

• Tungsten (W): 2.5–3.5% (synergizes with Mo for localized corrosion resistance).

• Iron (Fe): 2–6%, Cobalt (Co): ≤2.5% (trace elements).

• Carbon (C), Manganese (Mn), Silicon (Si), Sulfur (S), Phosphorus (P), Vanadium (V): Minimized to enhance weldability and reduce intermetallic phase formation.

Physical and Mechanical Properties:

• Tensile Strength: ~100 ksi (690 MPa).

• Yield Strength: ~45 ksi (310 MPa).

• Elongation: ~45% (excellent ductility).

• Thermal Conductivity: 9.8 W/m·K (at 100°C).

• Coefficient of Thermal Expansion: 12.2 μm/m·K (20–100°C).

• Density: 8.69 g/cm³.

• Non-Magnetic: Suitable for sensitive applications.

Application:

• Heat Exchangers in Petrochemical Plants: Alloy C22’s resistance to chloride-induced corrosion and its high-temperature strength make it suitable for use in heat exchangers in petrochemical refining processes, such as hydroprocessing, alkylation, and dehydrogenation processes.
• Sulfur Recovery Units: In sulfur recovery plants, where acid gases like hydrogen sulfide and sulfur dioxide are common, Alloy C22 tubes are used in heat exchangers to prevent corrosion in these aggressive environments.
• Pharmaceutical Manufacturing: Alloy C22’s excellent corrosion resistance and biocompatibility make it suitable for heat exchangers in pharmaceutical and biotechnology applications. It can handle aggressive cleaning agents and sterilization processes, ensuring long-term, reliable operation in these high-purity environments.
• Drug Processing: In the drug manufacturing process, where heat exchangers are used to control the temperature of various fluids and chemicals, Alloy C22 offers corrosion resistance, even in highly acidic or chloride-containing environments.