Hastelloy C-276 and Hastelloy C-22 are nickel-molybdenum-chromium alloys designed for severe corrosion environments. Both are widely considered for chemical processing, pollution-control systems and industrial equipment exposed to aggressive media.

Hastelloy C-276 is widely used for broad resistance to reducing and oxidizing environments, while Hastelloy C-22 is particularly valued for resistance to oxidizing aqueous media and localized corrosion. The correct choice depends on the chemical environment and the required fabrication condition.

1. Alloy Design

Hastelloy C-276 contains nickel, molybdenum, chromium and tungsten, with controlled iron and carbon levels. Its composition is designed to resist a wide range of corrosive chemicals.

Hastelloy C-22 contains a high chromium level together with molybdenum and tungsten. This balance provides strong resistance to oxidizing environments and helps reduce susceptibility to pitting, crevice corrosion and stress corrosion cracking in many service conditions.

The two grades are related, but they should not be treated as interchangeable without checking the operating environment and specification.

2. Corrosion Resistance Comparison

Hastelloy C-276

C-276 is frequently selected for equipment exposed to mixed chemical environments, including combinations of oxidizing and reducing conditions. It is used in systems where process chemistry may vary or where broad corrosion resistance is important.

Hastelloy C-22

C-22 is commonly selected for highly oxidizing aqueous environments and applications where localized corrosion resistance is a major concern. It is widely considered in chemical processing and pollution-control equipment.

Actual corrosion performance depends on temperature, chemical concentration, impurities, aeration and process conditions. Laboratory data or corrosion testing may be required for critical applications.

3. Weldability and Fabrication

Both alloys are available in forms suitable for industrial fabrication, including plate, sheet, pipe, tube, bar and other products depending on supplier capability and specification.

Important procurement considerations include:

• Welding procedure qualification
• Heat input and interpass temperature control
• Post-weld corrosion requirements
• Surface cleaning and contamination prevention
• Product thickness and heat-treatment condition
• Non-destructive testing requirements

The selected grade should be matched to the final component and not chosen solely from a general corrosion-resistance chart.

4. Typical Applications

Hastelloy C-276 is used in:

• Chemical processing equipment
• Flue-gas desulfurization systems
• Scrubbers and pollution-control equipment
• Acid processing systems
• Industrial piping and heat exchangers

Hastelloy C-22 is used in:

• Chemical process equipment
• Pharmaceutical processing systems
• Pollution-control equipment
• Chlorination and oxidizing chemical service
• Corrosion-resistant piping and fabricated components

5. C-276 or C-22: Procurement Checklist

Before requesting a quotation, provide:

1. Chemical composition of the service medium
2. Operating temperature and pressure
3. Concentration and expected contaminants
4. Required product form and dimensions
5. Applicable ASTM, ASME or project specification
6. Welding and surface-finish requirements
7. Inspection, testing and documentation requirements

Conclusion

Hastelloy C-276 and C-22 are both advanced corrosion-resistant nickel alloys, but their alloy chemistry and application emphasis differ. C-276 is often considered for broad, mixed-environment corrosion resistance, while C-22 is frequently evaluated for oxidizing aqueous service and localized corrosion control.

For grade selection, product availability and custom material requirements, contact AlloysFactory.

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