Hastelloy C276 (UNS N10276 / DIN 2.4819) is the most widely specified nickel-molybdenum-chromium alloy in severe corrosion service. Developed specifically to resist the broadest possible range of aggressive chemical environments, from strongly reducing acids to moderately oxidising media, Hastelloy C276 remains the benchmark corrosion-resistant alloy for chemical processing, oil and gas, flue gas desulfurisation (FGD), and pharmaceutical applications worldwide. Its exceptionally low carbon and silicon content minimises grain boundary precipitation during welding, enabling use in the as-welded condition without post-weld heat treatment in most service environments. Browse our complete Hastelloy Products range to explore all available product forms.
Hastelloy C276 Chemical Composition (UNS N10276 / ASTM B622)
Hastelloy C276 chemical composition is defined under ASTM B622, B619, and B626. The alloy derives its outstanding corrosion resistance from a combination of high molybdenum (15–17 wt%), chromium (14.5–16.5 wt%), and tungsten (3–4.5 wt%), with nickel as the primary matrix element. Carbon is controlled to a maximum of 0.01 wt%, one of the tightest carbon limits of any commercial nickel alloy to suppress sensitisation and intergranular attack in the heat-affected zone of welds.
| Element | Min (wt%) | Max (wt%) | Nominal (wt%) | Role | Significance |
| Nickel (Ni) | 57.0 | Balance | ~57% | Matrix | Base element; non-magnetic |
| Molybdenum (Mo) | 15.0 | 17.0 | 16% | Primary corrosion | Reducing acid resistance, pitting |
| Chromium (Cr) | 14.5 | 16.5 | 15.5% | Oxidation | Oxidising acid and high-temp resistance |
| Iron (Fe) | 4.0 | 7.0 | 5.5% | Diluent | Cost reduction; minor effect |
| Tungsten (W) | 3.0 | 4.5 | 3.75% | Solid solution | Enhances reducing acid resistance |
| Cobalt (Co) | — | 2.5 max | — | Trace | Controlled impurity |
| Carbon (C) | — | 0.01 max | — | Weld control | Ultra-low; prevents sensitisation |
| Manganese (Mn) | — | 1.0 max | — | Impurity | Controlled for cleanliness |
| Silicon (Si) | — | 0.08 max | — | Weld control | Low Si = better weld ductility |
| Vanadium (V) | — | 0.35 max | — | Trace | Impurity limit |
| Phosphorus (P) | — | 0.04 max | — | Impurity | Low for weld quality |
| Sulphur (S) | — | 0.03 max | — | Impurity | Controlled for hot workability |
Hastelloy C276 Physical Properties
The following physical properties apply to Hastelloy C276 (UNS N10276) in the solution-annealed condition at room temperature.
| Property | Value | Unit / Notes |
| Density | 8.89 | g/cm³ (0.321 lb/in³) |
| Melting Range | 1325 – 1370 | °C (2415–2500°F) |
| Specific Heat | 427 | J/kg·°C at 20°C |
| Thermal Conductivity | 10.2 | W/m·°C at 20°C |
| Electrical Resistivity | 1.30 | µΩ·m at 20°C |
| Modulus of Elasticity | 205 | GPa (29.7 × 10⁶ psi) |
| Magnetic Permeability | 1.0004 | Essentially non-magnetic |
| Coefficient of Thermal Expansion | 11.2 | µm/m·°C (20–100°C) |
Hastelloy C276 Mechanical Properties: Solution Annealed Condition
Hastelloy C276 tensile strength and other mechanical properties in the solution-annealed condition meet the minimum requirements of ASTM B622 (sheet/plate/strip), B619 (welded pipe), and B626 (welded tube). Properties shown are minimum specification values; individual heats typically exceed these on the Material Test Report (MTR).
| Property | Metric (SI) | Imperial | ASTM Minimum |
| Ultimate Tensile Strength (UTS) | 690 MPa | 100 ksi | 690 MPa |
| 0.2% Proof Strength (Yield) | 283 MPa | 41 ksi | 283 MPa |
| Elongation (in 50 mm) | 40% | 40% | 40% min |
| Hardness (Rockwell B) | 100 HRB max | 100 HRB max | 100 HRB |
| Hardness (Brinell) | 241 HB max | 241 HB max | — |
| Impact Strength (Charpy V) | >100 J | >74 ft·lbf | — |
Unlike precipitation-hardened nickel alloys such as Inconel 718, Hastelloy C276 achieves its strength entirely through solid-solution strengthening. There is no aging heat treatment requirement, simplifying procurement, fabrication, and quality assurance.
Hastelloy C276 Corrosion Resistance
Hastelloy C276 corrosion resistance is the defining characteristic of this alloy and the primary reason for its specification across chemical processing, oil and gas, and environmental engineering applications. The combination of high molybdenum and tungsten provides outstanding resistance in reducing environments, while chromium provides adequate performance in moderately oxidising conditions.
Hydrochloric Acid (HCl)
Hastelloy C276 hydrochloric acid resistance is exceptional. The alloy resists all concentrations of HCl at temperatures up to approximately 40°C and dilute concentrations (below 2%) up to boiling point. This is the single most demanding test environment for any corrosion-resistant alloy, and C276 outperforms all grades of stainless steel and most nickel alloys in this medium. ISO-corrosion diagrams show C276 performing well where 316L stainless steel shows corrosion rates exceeding 1.0 mm/year.
Sulfuric Acid (H₂SO₄)
Hastelloy C276 sulfuric acid resistance covers the full concentration range from dilute to concentrated H₂SO₄ at ambient conditions, and a wide range of concentrations at elevated temperatures. The alloy is particularly valuable in mixed acid streams where H₂SO₄ is combined with oxidising contaminants (e.g., ferric chloride or cupric chloride) that would attack pure reducing-resistant alloys.
Oxidising and Reducing Mixed Environments
One of the most significant advantages of Hastelloy C276 over many speciality alloys is its ability to tolerate swings between oxidising and reducing conditions within the same process stream. Chemical plant upsets, process changeovers, and mixed-acid streams often expose piping and vessels to both regimes simultaneously. C276 provides a reliable safety margin in these unpredictable environments.
Key Corrosive Environments Where C276 is Specified
- Hydrochloric acid (HCl) — all concentrations below 40°C; dilute HCl to boiling
- Sulfuric acid (H₂SO₄) — wide concentration range; superior to Inconel 625 in hot dilute H₂SO₄
- Wet chlorine gas — excellent; resists chlorine and hypochlorite below ~70°C
- Ferric chloride (FeCl₃) and cupric chloride (CuCl₂) — oxidising chloride pitting solutions
- Phosphoric acid — good resistance across concentrations to boiling
- Acetic, formic, and other organic acids — excellent across a broad range
- Seawater and saline solutions — high PREN; resistant to crevice and pitting attack
- Sour gas (H₂S + CO₂ + Cl⁻) — NACE MR0175 / ISO 15156 compliant
- Flue gas condensate — FGD scrubber service with SO₂, HCl, and HF in solution
Note: Hastelloy C276 is NOT recommended for concentrated nitric acid, fuming nitric acid, or strongly oxidising media at elevated temperatures for those environments, specify Hastelloy C-22 or Hastelloy C-2000.
Hastelloy C276 vs C22 Comparison
The Hastelloy C276 vs C22 comparison is the most frequently asked question in corrosion-resistant alloy selection. Both alloys are based on the Ni-Cr-Mo system; the key difference lies in the oxidising-to-reducing balance of the service environment.
| Property / Environment | Hastelloy C276 | Hastelloy C22 |
| UNS Number | N10276 | N06022 |
| Chromium % | 14.5–16.5 | 20.0–22.5 (higher) |
| Molybdenum % | 15.0–17.0 | 12.5–14.5 (lower) |
| Tungsten % | 3.0–4.5 | 2.5–3.5 |
| Reducing Acid Resistance | Excellent — primary strength (high Mo + W) | Very Good |
| Oxidising Acid Resistance | Good | Excellent — primary strength (high Cr) |
| Mixed Acid Environments | Excellent | Excellent — slightly broader oxidising range |
| HCl Resistance | Superior | Very Good |
| Concentrated HNO₃ Resistance | Limited — not recommended | Good |
| Weldability | Excellent; no PWHT required | Excellent; no PWHT required |
| ASTM Specifications | B622 / B619 / B626 / B574 | B622 / B619 / B626 / B574 |
| Typical Application | Reducing & mixed chemical environments, HCl-bearing streams | Oxidising + reducing environments, waste treatment, mixed acids |
| Select When… | Process is predominantly reducing with chloride exposure | Process has significant oxidising component (HNO₃, Cl₂, FeCl₃) or alternating regimes |
Hastelloy C276 vs Inconel 625 Comparison
The Hastelloy C276 vs Inconel 625 selection question frequently arises in offshore, chemical, and FGD applications, where both alloys are commonly available and specified. The decision turns on temperature range, fabrication complexity, and the specific corrosive media involved.
| Property | Hastelloy C276 (N10276) | Inconel 625 (N06625) |
| Primary Alloying | Ni-Mo-Cr-W (Mo 16%, Cr 15.5%) | Ni-Cr-Mo-Nb (Mo 9%, Cr 21%, Nb 3.6%) |
| Corrosion Focus | Reducing & mixed acid chemical service | Broad corrosion + high temperature structural |
| HCl Resistance | Superior (Mo 16%) | Good (Mo 9%) |
| H₂SO₄ Resistance | Excellent — hot dilute H₂SO₄ | Good |
| Pitting Resistance (PREN) | ~70 (very high) | ~51 (high) |
| Max Service Temperature | 1038°C (1900°F) — oxidation | 982°C (1800°F) — Gr.1 / 593°C Gr.2 creep |
| High-Temp Structural Strength | Moderate | Superior (Nb solid solution hardening) |
| Weldability / PWHT | Excellent; no PWHT required | Excellent; no PWHT required |
| Cost | Typically higher (higher Mo content) | Lower — more widely stocked |
| Select When… | Severe reducing acid / mixed chemical environments dominate | Offshore, subsea, high-temp service, or where fabrication cost matters |
Hastelloy C276 Temperature Resistance and Performance
Hastelloy C276 temperature resistance covers a broad service range. In aqueous corrosion service, the alloy performs from cryogenic temperatures (below -196°C with appropriate impact testing) up to approximately 400°C before specific corrosion resistance begins to diminish in certain media. At elevated temperature in air or combustion atmospheres, oxidation resistance extends to 1038°C (1900°F).
- Cryogenic service: Suitable with impact testing to -196°C
- Ambient to 400°C: Full corrosion resistance in most specified media
- 400°C – 650°C: Elevated temperature use generally limited to non-corrosive or mildly corrosive environments; consult NACE guidelines for sour gas service
- Above 650°C to 1038°C: Oxidation resistance in air; suitable for furnace components, catalyst support hardware
- ASME Boiler & Pressure Vessel Code (ASME B31.3 / ASME Section VIII) allowable stress values available up to 815°C
Important note: Hastelloy C276 should not be exposed to temperatures between 540–760°C for extended periods in service — this range promotes precipitation of intermetallic phases (mu-phase and sigma-phase) that can reduce toughness and ductility.
Hastelloy C276 Weldability and Fabrication
Hastelloy C276 weldability is one of the alloy’s most commercially important properties. The ultra-low carbon (0.01% max) and silicon (0.08% max) content minimises carbide and silicide precipitation in the weld heat-affected zone, allowing the alloy to be used in the as-welded condition for most service environments without requiring post-weld solution annealing.
Welding Processes
- GTAW (TIG) — preferred for root passes and thin-wall pipe; use ERNiCrMo-4 filler (AWS specification) which matches C276 nominal chemistry
- GMAW (MIG) — suitable for thicker sections
- SMAW — E NiCrMo-4 covered electrode
- SAW (submerged arc) — not generally recommended; can dilute alloy content
Fabrication Notes
- Solution anneal after severe cold working: 1121°C (2050°F) minimum, water quench
- Machining: moderate difficulty — work hardening rate is significant; use sharp tooling, positive rake angles, and adequate coolant flow; reduce cutting speeds vs 316L stainless by approximately 30%
- Forming: Cold forming is feasible with standard tooling; allow for springback; solution anneal if >15% cold reduction
- Avoid contamination with iron particles — clean all tooling and contact surfaces before fabrication
Hastelloy C276 machinability: CNC turning and milling are standard. Work hardening requires lower feed rates, higher cutting speeds, and more frequent tool changes than 316L stainless steel. Flood coolant is mandatory. For drilling, use stub-length drills to minimise deflection. Estimated machining cost premium vs 316L stainless: 2–3×.
Hastelloy C276 Industry Applications
Hastelloy C276 applications span every major process industry segment where corrosive chemicals are handled at elevated temperatures or pressures:
Chemical Processing
- Reactors, columns, and heat exchangers handling HCl, H₂SO₄, phosphoric acid, and mixed-acid streams
- Chlorinated solvent production — vinyl chloride, methylene chloride, chlorobenzene
- Acid concentration plants and acid recovery systems
- Pickling and etching equipment
Oil and Gas — Upstream and Downstream
- Sour gas (H₂S + CO₂ + Cl⁻) wellhead equipment, tubing hangers, and Christmas tree components
- Downhole completion tools in high-chloride, high-CO₂ wells
- Process vessels and heat exchangers handling crude containing naphthenic acid
- FPSO topside piping in aggressive seawater service
Flue Gas Desulfurisation (FGD)
Hastelloy C276 FGD applications represent one of the highest-volume uses of the alloy. Coal-fired and industrial plant scrubbers handle wet flue gas containing dissolved SO₂, HCl, HF, and fly ash particulates at temperatures of 50–80°C — a uniquely aggressive mixed-acid environment that eliminates rubber-lined carbon steel, fibreglass, and most stainless grades. C276 provides long-term service life for absorber vessels, ducts, spray lances, and mist eliminators.
Pulp and Paper
- Chlorine dioxide bleaching circuits — digester and bleach plant equipment
- White liquor and green liquor handling systems
- Evaporator tubes in the black liquor circuit
Pharmaceutical and Fine Chemical
- Reactor vessels, agitators, and pipework in multi-purpose API manufacturing plants
- USP-grade process piping where cross-contamination prevention is required
- Highly corrosive intermediates and specialty chemical synthesis
Marine and Environmental
- Seawater handling and desalination components
- Offshore platform systems in aggressive splash zone environments
- Industrial and municipal wastewater treatment, scrubbers, oxidation vessels
Hastelloy C276 Available Product Forms
Kalpataru Piping supplies the complete range of Hastelloy C276 product forms in accordance with ASTM B622 (sheet/plate/strip), B619 (welded pipe), B626 (welded tube), and B574 (bar). All products are supplied with certified Material Test Reports (MTRs), and third-party inspection is available on request:
- Hastelloy C276 Pipes & Tubes — seamless and welded, small bore to large diameter
- Hastelloy C276 Pipe & Tube Specifications — full dimensional and schedule data
- Hastelloy C276 Plates & Sheets — ASTM B622 hot-rolled and cold-rolled
- Hastelloy C276 Round Bars & Wires — ASTM B574 bar; B619 weld wire
- Hastelloy C276 Flanges — ASME B16.5 / B16.47 all types
- Hastelloy C276 Fasteners — studs, bolts, nuts, washers
- Hastelloy C276 Buttweld Fittings — elbows, tees, reducers, caps
Conclusion
Hastelloy C276 (UNS N10276 / DIN 2.4819) remains the benchmark nickel alloy for severe chemical corrosion service after more than five decades of industrial use. Its combination of high molybdenum, chromium, and tungsten content together with ultra-low carbon and silicon delivers reliable, long-service performance in the most aggressive reducing, mixed-acid, and chloride-bearing environments encountered in chemical, oil and gas, FGD, pulp and paper, and pharmaceutical applications.
When evaluating Hastelloy C276 against Hastelloy C-22 or Inconel 625: C276 is the choice for predominantly reducing and HCl-dominated environments; C-22 is the step-up when significant oxidising acids (HNO₃, wet Cl₂) are also present; Inconel 625 is the more economical selection for offshore and high-temperature structural applications where its Nb content and ASTM B444 seamless tube availability are advantageous.
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