Hastelloy C-22 vs. C-276: The Chemical Industry's Toughest Choice
Inside chemical plants, the argument over C-22 versus C-276 has been running for thirty years. Both are nickel-chromium-molybdenum alloys with elite corrosion resistance. The difference is six elements of chemistry — and knowing which one your process needs saves either money or equipment.
The chemistry gap in one line
C-276 (UNS N10276): 16% Mo, 4% W, ~15.5% Cr. C-22 (UNS N06022): 13% Mo, 3% W, ~22% Cr. In plain terms — C-276 bets on molybdenum, C-22 bets on chromium.
What that means in the plant
- Reducing acids (hot HCl, sulfuric without oxidizers): molybdenum rules. C-276 has the edge — it's the historical champion of reducing service.
- Oxidizing media (ferric chloride, cupric chloride, nitric-bearing mixes, wet chlorine gas, hypochlorite): chromium rules. C-22's 22% Cr makes it clearly superior — this is why bleach plants and FGD systems standardized on it.
- Mixed or upset-prone streams: real processes drift between oxidizing and reducing. C-22's balanced chemistry tolerates excursions better, which is why many EPCs now specify it as the "insurance" grade.
- Pitting/crevice (PREN): C-276 ≈ 68, C-22 ≈ 65 — effectively a tie. Both laugh at seawater.
Fabrication and price
Both weld well with matching fillers (ERNiCrMo-4 / ERNiCrMo-10) and both resist weld-zone corrosion better than nearly anything else on the market. C-22 is slightly more resistant to intermetallic precipitation during welding — a real advantage on heavy sections. Pricing is usually within a few percent; availability of the exact product form often decides.
Our honest recommendation
If your medium is a known, stable reducing acid — C-276, the proven answer. If your stream is oxidizing, mixed, or simply not fully characterized — C-22 is the safer default. When a customer sends us an analysis that contains both chlorides and oxidizing ions, we quote C-22.