Hastelloy C-276 is the premium corrosion-resistant alloy — used when 316 stainless fails, when duplex fails, when Inconel fails. Its molybdenum + tungsten content creates unmatched resistance to pitting, crevice corrosion, and stress-corrosion cracking across the broadest chemistry range. Cost is high (3-5× Inconel 625), but for the applications where it's needed, alternatives don't exist.
| Element | % by weight | Role |
|---|---|---|
| Nickel | Balance (~57%) | Matrix, corrosion resistance foundation |
| Chromium | 14.5-16.5% | Passive layer formation |
| Molybdenum | 15-17% | Pitting resistance in chlorides (the key element) |
| Tungsten | 3-4.5% | Strength, improved localized corrosion resistance |
| Iron | 4-7% | Matrix modifier |
| Cobalt | ≤2.5% | Trace |
| Carbon (max) | 0.01% | Low enough to prevent sensitization |
The 15-17% molybdenum content is what sets C-276 apart. Compared to Inconel 625 (8-10% Mo), C-276 has nearly twice the molybdenum — providing dramatically better resistance to pitting and crevice corrosion in chloride-containing environments.
Scrubbers in coal-fired power plants. Extremely corrosive mix of sulfuric acid, hydrochloric acid, chlorides, and abrasive fly ash. C-276 is the industry standard material for wetted surfaces.
Wet chlorine gas, chloride solvents, mixed-acid chemistries. C-276 handles these where 316, duplex, and Inconel 625 all fail.
Downhole tools in sour wells (high H₂S + chloride + high temperature). C-276 resists sulfide stress cracking better than any competing alloy.
Complex multi-chemistry environments where the reactor must handle whatever the pharmacist specifies over a 20-year lifespan. C-276 is chosen as the "universal" material.
Hypochlorite and chlorine dioxide environments. C-276 is standard for bleach plant equipment.
| Property | Value |
|---|---|
| Tensile strength | 760 MPa (annealed) |
| Yield strength | 370 MPa |
| Elongation | 40% |
| Hardness | 90 HRB |
| Density | 8.89 g/cm³ |
| Max service temp (structural) | 675 °C |
| Machinability rating | ~10-12% |
| Weldability | Excellent (matching filler or Inconel 686) |
Machining C-276 is difficult — even harder than Inconel. Expect:
Common workflow for critical parts: rough machine at high rates, finish at very low rates with fresh carbide, add grinding/EDM for the tightest tolerances.
C-276 is often over-specified by consultants playing it safe with "premium" material:
C-276 is the right choice when multiple corrosion modes are present (pitting + crevice + SCC + general), when chemistry is cycling/uncertain, or when 316/Inconel have failed historically in the application.
Email [email protected] with service conditions. We stock C-276 bar and plate in common sizes. Aerospace-certified material available on request (2-3 week lead).
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