Hastelloy C Chemical Resistance Chart: Properties & Applications

Hastelloy C is a family of nickel-chromium-molybdenum (Ni-Cr-Mo) superalloys developed and manufactured by Haynes International, Inc.³（The name "Hastelloy" is a registered trademark of Haynes International; the "C" designation identifies a subfamily of grades sharing a high-nickel, molybdenum, and chromium base composition.

What sets Hastelloy C alloys apart from most corrosion-resistant metals is their ability to perform in both oxidizing and reducing chemical environments — a dual capability that stainless steel and many other nickel alloys cannot reliably offer. This makes them the material of choice in processes where the chemical environment is aggressive, mixed, or unpredictable.

Hastelloy C alloys are widely used across chemical processing, pharmaceutical manufacturing, semiconductor wet processing, pollution control, and nuclear applications. Their electrical and thermal conductivities are significantly lower than carbon steel, while electrical resistivity and thermal expansion rates are considerably higher — properties that are important to account for in system design.

The Hastelloy C family includes several distinct grades. The three most commonly specified in industrial applications are C-276, C-22, and C-4. Each has a different composition and a different corrosion performance profile 

Hastelloy C alloys share high strength and toughness as a family, but their work hardening tendency makes machining more demanding than standard austenitic stainless steels — requiring slower speeds, carbide tooling, and in cold-working applications, intermediate annealing between stages.

A defining characteristic of the family is corrosion resistance in the weld heat-affected zone (HAZ). Most Hastelloy C grades resist the formation of grain-boundary precipitates in the HAZ, meaning welded assemblies can typically be placed into service without post-weld heat treatment. This is a significant practical advantage in fabricated chemical process equipment. 

The table below lists representative physical and mechanical properties for the Hastelloy C family. Values shown are for for the two most commonly specified grades — C-276 and C-22. The differences in composition drive meaningful differences in corrosion performance: C-22's higher chromium and lower molybdenum make it superior in oxidizing media, while C-276's higher molybdenum gives it an edge in reducing environments. Values are for mill-annealed wrought product. C-276 ASTM minimums sourced from Haynes International and ASTM B622;¹ C-22 values from the Haynes International C-22 datasheet and brochure.²refer to the respective Haynes International datasheets for grade-specific values.

Thanks to their broad corrosion resistance and mechanical reliability, Hastelloy C alloys are specified wherever process conditions are too aggressive for stainless steel. Typical applications include: 

• Chemical processing: reactors, heat exchangers, and columns handling sulfuric acid, hydrochloric acid, and chlorinated solvents
• Pharmaceutical & agrochemical: equipment in contact with organic acids, oxidizing agents, and reaction byproducts
• Semiconductor & wet processing: chemical delivery systems and wet bench components in aggressive acid/base environments
• Pollution control (FGD): flue gas desulfurization systems handling acidic gases and slurries
• Pulp & paper: bleach plant equipment exposed to chlorine-based compounds
• Nuclear: structural components requiring stability in high-radiation environments

The chart below shows general Hastelloy C family compatibility with common industrial chemicals at ambient temperature. Ratings are not grade-specific — actual performance varies between C-276, C-22, and C-4 depending on the chemical, concentration, and temperature. Use this as an initial screening reference only.

What is the difference between Hastelloy C-276, C-22, and C-4?

C-276 is the most widely used grade, offering strong resistance to both oxidizing and reducing acids, chlorides, and pitting. C-22 adds improved resistance to oxidizing media and is often used as weld filler where C-276 weld joints face attack. C-4 is optimized for thermal stability at 650–1040°C with reduced grain boundary precipitation risk at elevated temperatures.

Is Hastelloy C-276 resistant to hydrochloric acid?

Yes, at low concentrations and moderate temperatures — but both grade and conditions matter significantly. C-22 laboratory data shows corrosion rates below 0.1 mm/year at 1% HCl up to ~93°C, and below 0.01 mm/year at 5% HCl at 38°C.² Above 5% concentration, rates climb sharply with temperature: at 5% HCl and 66°C, C-22 reaches 0.44 mm/year; at 10% and 66°C, 0.98 mm/year.² C-276's higher molybdenum content gives it a comparable profile in reducing HCl environments.¹ Neither grade is recommended for concentrated HCl at elevated temperatures. Always validate under your actual process conditions — concentration, temperature, and any co-contaminants all affect the outcome.

How does Hastelloy C compare to AISI 316 stainless steel?

Hastelloy C alloys significantly outperform 316 SS in chloride-containing environments, reducing acids, and mixed oxidizing/reducing media. The trade-off is cost — Hastelloy C alloys are considerably more expensive and work-harden faster than 316. For mild chemical exposure, 316 SS is usually sufficient; for aggressive or mixed-media environments, Hastelloy C is the appropriate choice. See our AISI 316 chemical resistance chart for a side-by-side comparison.

Which Hastelloy C grade should I use for my application?

Start with C-276 for most general chemical processing environments involving mixed media, chlorides, or organic acids. Consider C-22 if your process involves strongly oxidizing conditions or if weld joint corrosion is a concern. Specify C-4 when sustained service above 650°C is a requirement. If you need help narrowing down the selection, contact LORRIC's technical team with your chemical name, concentration, and operating temperature.