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Hastelloy C-276 (UNS N10276) and C-22 (UNS N06022) share identical 690 MPa minimum tensile strength, but their corrosion profiles differ significantly. C-276 with 16% molybdenum excels in strongly reducing acids (HCl, H2SO4), while C-22 with 22% chromium provides superior resistance in oxidizing acids, mixed acid environments, and wet chlorine gas. C-22 is often called the upgrade from C-276 due to its broader overall corrosion resistance.
| Property | Hastelloy C-276 | Hastelloy C-22 |
|---|---|---|
| UNS | N10276 | N06022 |
| W.Nr. | 2.4819 | 2.4602 |
| Tensile Strength (RT) | 690 MPa (100 ksi) min. | 690 MPa (100 ksi) min. |
| Yield Strength (RT) | 283 MPa (41 ksi) min. | 310 MPa (45 ksi) min. |
| Elongation | 40% min. | 45% min. |
| Max Service Temperature | 1038°C (1900°F) | ~1050°C |
| Density | 8.89 g/cm³ | 8.69 g/cm³ |
| Chromium Content | 16% | 22% |
| Molybdenum Content | 16% | 13% |
| Tungsten Content | 4% | 3% |
| Medium | Hastelloy C-276 | Hastelloy C-22 |
|---|---|---|
| Oxidizing acids (HNO₃, wet Cl₂) | Good | Excellent (higher Cr) |
| Reducing acids (HCl, H₂SO₄) | Excellent (higher Mo) | Very good |
| Mixed acid environments | Very good | Excellent |
| Wet chlorine gas | Good | Significantly better |
| Pitting/crevice corrosion | Very good | Excellent (higher Cr) |
| Weld HAZ corrosion | Susceptible | Superior — commonly used as filler metal |
| Intergranular corrosion | Good | Excellent |
Strongly reducing environments are involved (hot HCl, concentrated H2SO4), existing specifications call for C-276, or when budget is a factor — C-276 is more widely available and often lower cost. Its 16% molybdenum content gives it an edge in pure reducing acid service.
Oxidizing environments, mixed acid service, wet chlorine gas, or welded assemblies are involved. C-22 is commonly used as weld filler metal due to superior weld HAZ corrosion resistance. Choose C-22 when the broadest possible corrosion resistance across both oxidizing and reducing conditions is needed.
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