In industries like chemical processing, marine engineering, and oil & gas, selecting the right "armor" against corrosion is critical. Hastelloy C-22 (UNS N06022) and Hastelloy C-276 (UNS N10276) are the two most prominent "Kings" of nickel-chromium-molybdenum alloys.
But which one is better for your specific project? At Gnee Steel, we help engineers worldwide navigate these technical choices to ensure safety and durability. This guide breaks down everything you need to know about C-22 vs. C-276.
1. Chemical Composition: The Battle of Cr vs. Mo
While both are Ni-Cr-Mo alloys, the secret to their performance lies in the slight adjustment of Chromium and Molybdenum.
| UNS / W.Nr | UNS / W.Nr | Ni | Cr | Mo | W | Key Feature |
| Hastelloy C-22 | N06022 / 2.4602 | Balance | 22% | 13% | 3% | High Chromium for Oxidation |
| Hastelloy C-276 | N10276 / 2.4819 | Balance | 16% | 16% | 4% | High Molybdenum for Reduction |
C-22 contains significantly more Chromium, enhancing its resistance to oxidizing environments.
C-276 has a higher Molybdenum and Tungsten content, making it superior in reducing environments.
2. Corrosion Resistance: Which Environment Are You In?
Hastelloy C-22: The Master of Oxidation
Thanks to its high chromium content, C-22 provides exceptional resistance to oxidizing aqueous media, including wet chlorine and mixtures containing nitric acid or oxidizing acids with chloride ions. It is also highly resistant to weld-heat-affected zone attack.
Hastelloy C-276: The All-Rounder for Reduction
C-276 is the "industry standard" for a reason. Its high molybdenum content makes it incredibly resistant to pitting and crevice corrosion in reducing media like hydrochloric acid, phosphoric acid, and sulfuric acid. It also performs exceptionally well in sour gas (H2S) environments.
Gnee Steel Professional Tip: If your process involves fluctuating conditions (both oxidizing and reducing), C-22 often offers better "overall" corrosion resistance, but C-276 remains the most cost-effective and proven solution for most general chemical applications.
3. Mechanical & Physical Properties
Both alloys are solid-solution strengthened and offer similar mechanical strength. However, their temperature limits differ slightly in pressure vessel applications:
C-22: Excellent stability from cryogenic temperatures up to 1250°F (677°C).
C-276: Generally used up to 1000°F (538°C) in corrosive environments.
4. Common Applications & Standards
Gnee Steel supplies both C-22 and C-276 for high-stakes industries:
Chemical Processing: Reactors, heat exchangers, and evaporators.
Pollution Control: Flue gas desulfurization (FGD) systems.
Pharmaceuticals: Equipment requiring high-purity and corrosion resistance (C-22 is often preferred here).
Waste Treatment: Hazardous waste incineration and wastewater processing.
International Standards We Follow:
Seamless Pipe: ASTM B622
Plate/Sheet: ASTM B575
Bar Stock: ASTM B574
Forgings: ASTM B564
Why Partner with Gnee Steel?
Navigating the complexities of nickel-based alloys requires a supplier with technical depth. Gnee Steel isn't just a distributor; we are your technical partner in the nickel alloy industry.
Strict Quality Control: Every shipment comes with a full MTC (Material Test Certificate) according to EN 10204 3.1, ensuring 100% traceability.
Extensive Inventory: We maintain a large stock of C-22 and C-276 in various forms, including plates, pipes, round bars, and flanges.
Global Logistics: Our team handles complex shipping requirements for clients in Europe, the Americas, and Southeast Asia, ensuring on-time delivery for your critical projects.
Conclusion: The Selection Verdict
Choose Hastelloy C-22 if your project involves strong oxidizing acids, high-temperature oxidizing environments, or if you need the highest level of protection against crevice corrosion.
Choose Hastelloy C-276 if you are dealing with aggressive reducing acids (like HCl), need a proven "workhorse" with 50 years of data, or require a more cost-effective solution for general strong corrosion.
Still unsure which alloy is right for your environment?
Contact the Gnee Steel engineering team today! We provide free material selection consultations and competitive quotes for your next project.
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