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Certifications: EN 10204 3.1 / 3.2 material test certificates, PMI verification, and complete export documentation packages.
Hastelloy
C-276
(UNS N10276)
A world-class technical reference for EPC contractors, chemical process engineers, procurement heads, and TPI inspection agencies specifying Hastelloy C-276 nickel-molybdenum-chromium alloy — covering alloy metallurgy, its position as one of the most broadly corrosion-resistant commercial alloys available, the low-carbon/low-silicon composition enabling as-welded service without post-weld heat treatment, and the QC and documentation discipline required for critical chemical process and pollution control equipment supply.
Key Properties
& Selection Logic
Hastelloy C-276 (UNS N10276) is a nickel-molybdenum-chromium- tungsten alloy widely regarded as one of the most broadly corrosion-resistant commercial engineering alloys available — performing well in both strongly oxidizing and strongly reducing environments, a combination few other single alloys achieve.
1.1 — What Hastelloy C-276 (UNS N10276) Is
Hastelloy C-276 is a nickel-molybdenum-chromium alloy with a nominal composition of approximately 57% nickel, 15–17% molybdenum, 14.5– 16.5% chromium, 3–4.5% tungsten, and 4–7% iron, with the balance comprising minor elements — critically including a deliberately controlled low carbon content (≤0.010%) and low silicon content (≤0.08%), discussed in detail in Section 1.3, that distinguishes C-276 from its predecessor “Hastelloy C” and gives the alloy its modern practical weldability advantage. The high combined molybdenum and chromium content, together with the tungsten addition, gives C-276 an unusually broad corrosion resistance profile spanning both oxidizing environments (where the chromium content provides passivation) and reducing/non-oxidizing environments (where the molybdenum content provides resistance) — a combination that makes the alloy the default, “when in doubt” specification choice for the most chemically aggressive or chemically variable/unknown process environments in chemical engineering practice.
1.2 — Key Engineering Properties
Broadest Commercial Corrosion Resistance Range
Hastelloy C-276 resists a wider spectrum of corrosive chemicals — including wet chlorine gas, hypochlorite solutions, ferric and cupric chloride, hydrochloric acid at virtually all concentrations, sulphuric acid across a broad concentration/temperature range, and mixed acid environments containing both oxidizing and reducing species — than almost any other single commercial alloy, making it the standard “problem-solving” alloy specified where the process chemistry is unusually aggressive, variable, or not fully characterised.
Excellent Chloride Pitting, Crevice, and Stress Corrosion Cracking Resistance
Outstanding resistance to localized corrosion (pitting and crevice attack) in chloride-bearing environments, and excellent resistance to chloride stress corrosion cracking even at elevated temperature — substantially exceeding both standard austenitic stainless steel and duplex stainless steel performance in the most aggressive chloride service, and generally exceeding even Incoloy 825’s chloride performance (discussed in RR Hydraulic’s dedicated Incoloy 825 reference) in the most severe cases.
Excellent Wet Chlorine and Hypochlorite Resistance
A specific and industrially important property — C-276 resists wet chlorine gas and hypochlorite bleaching solutions where few other alloys perform adequately, making it the standard alloy for chlorine dioxide bleach plant equipment in the pulp and paper industry and for chlorine handling equipment generally.
Good Elevated-Temperature Strength
Reasonable mechanical strength retention at moderately elevated temperature, supporting pressure-containing equipment applications across a useful temperature range beyond ambient, though the alloy’s primary selection driver is corrosion resistance rather than high-temperature structural strength (unlike, for example, the Incoloy 800 family discussed in RR Hydraulic’s dedicated reference, which is specifically optimised for high-temperature strength and oxidation resistance).
1.3 — The Critical Role of Low Carbon and Low Silicon Content
Product Forms
& Composition Reference
Hastelloy C-276 is manufactured across tube, pipe, bar, and plate product forms, each governed by a specific ASTM/ASME standard. Full detail on related nickel alloys is available across our standards reference library.
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2.1 — Governing Standards
ASTM B575 / ASME SB-575 — Plate, Sheet, and Strip
Governs flat-rolled Hastelloy C-276 product — plate for pressure vessel fabrication, sheet and strip for general fabrication requiring the alloy’s corrosion performance.
ASTM B619 / ASME SB-619 — Welded Pipe
Governs welded nickel alloy pipe including C-276 — relevant for larger-diameter pipe applications where welded (rather than seamless) construction is specified.
ASTM B622 / ASME SB-622 — Seamless Pipe
Governs seamless nickel alloy pipe including C-276 — the primary specification for seamless pipe applications in chemical process piping.
ASTM B626 / ASME SB-626 — Welded Tube
Governs welded nickel alloy tube including C-276 — used for heat exchanger and general tubing applications where welded tube construction is specified.
ASTM B564 / B366 — Forgings and Forged Fittings
B564 governs forgings; B366 governs forged fittings — the specifications for forged flanges, fittings, and valve bodies in C-276 where forged (rather than bar-machined) construction is specified for critical pressure-boundary components.
NACE MR0175 / ISO 15156
Provides the material qualification framework for sour service use of Hastelloy C-276, including any applicable hardness limits — relevant where the alloy is specified for oil and gas process equipment with sour service exposure alongside its primary chemical process application.
2.2 — Chemical Composition and Mechanical Properties
| Element / Property | Value / Range |
|---|---|
| Nickel | Balance (~57%) |
| Molybdenum | 15.0–17.0% |
| Chromium | 14.5–16.5% |
| Tungsten | 3.0–4.5% |
| Iron | 4.0–7.0% |
| Carbon (max.) | 0.010% |
| Silicon (max.) | 0.08% |
| Tensile Strength | 760–900 MPa (typical, min. 690 MPa per spec) |
| Yield Strength | 350–430 MPa (typical, min. 283 MPa per spec) |
| Elongation | 45–65% |
2.3 — Comparison to Related Nickel-Molybdenum-Chromium Alloys
| Alloy | Key Distinguishing Feature | Best Suited For |
|---|---|---|
| Hastelloy C-276 (N10276) | The versatile, broadly corrosion-resistant baseline | Most aggressive mixed oxidizing/reducing environments, wet chlorine, general “unknown chemistry” problem-solving |
| Hastelloy C-22 (N06022) | Higher chromium, lower molybdenum than C-276 — improved oxidizing acid and localized corrosion resistance | Environments with a stronger oxidizing component than C-276 is optimised for |
| Hastelloy C-2000 (N06200) | Added copper — improved resistance to sulphuric acid specifically | Sulphuric acid-dominant process environments where C-276/C-22 are less optimal |
| Incoloy 825 (N08825) | Lower molybdenum, added copper — narrower but still broad acid resistance at lower cost | Sulphuric/phosphoric acid and sour service where the full C-276 cost premium is not justified |
Weld Practice
& Fabrication Guidance
Correct heat treatment and welding practice preserve Hastelloy C-276’s designed corrosion resistance — the alloy’s low carbon and silicon content provide a significant fabrication advantage, but correct process control remains essential.
3.1 — Solution Annealing Heat Treatment
Hastelloy C-276 is supplied in the solution-annealed condition — heated to approximately 1120–1150°C and rapidly cooled (typically water quenched for tube and pipe) to dissolve secondary phases into solid solution and establish the single-phase austenitic microstructure that provides the alloy’s designed corrosion resistance. This annealed condition is the standard, as-supplied condition for the large majority of C-276 applications — the alloy is not typically further hardened or aged, since its intended engineering value is broad-spectrum corrosion resistance rather than maximum achievable mechanical strength.
3.2 — Weld Practice
As-Welded Service Without Mandatory PWHT
As discussed in Section 1.3, C-276’s low carbon and silicon content allows the alloy to be welded and placed into service without mandatory post-weld solution annealing for the majority of applications — a significant practical fabrication advantage over higher-carbon alternatives and older alloy generations.
Matching Filler Metal Selection
Welding consumables matched to C-276 (ERNiCrMo-4 type filler metal, per AWS A5.14) are used to maintain corrosion resistance and mechanical property matching in the weld deposit — using a mismatched or lower-alloy filler metal compromises the weld’s corrosion resistance even if the base metal itself is correctly specified.
Heat Input Control
While C-276 does not require mandatory PWHT for typical fabrication welding, controlled heat input (avoiding excessive interpass temperature and heat accumulation) remains good practice to minimise any secondary-phase precipitation tendency and maintain optimal weld zone properties, particularly for multi-pass welds on thicker sections.
Cleanliness and Contamination Control
As with other nickel alloys, strict cleanliness control (removing oils, grease, marking materials, and avoiding contact with carbon steel tools or grinding debris) before and during welding is essential — contamination can cause weld defects and localized corrosion susceptibility in the completed weld.
3.3 — General Fabrication Considerations
Hastelloy C-276 machines and forms similarly to other high-nickel alloys — work-hardening during machining requires appropriate tooling and cutting parameters, similar to the machining considerations discussed in RR Hydraulic’s Titanium Grade 5 and Monel 400 references, though C-276 does not present the same degree of galling risk as titanium-on-titanium or Monel-on-Monel contact. Standard nickel-alloy fabrication practices — clean, controlled machining environments avoiding cross-contamination with lower-alloy materials, and appropriate tooling selection for the alloy’s work-hardening tendency — apply throughout C-276 component manufacture.
Industry Applications
& Documentation
RR Hydraulic maintains full traceability from certified nickel alloy heat to finished, tested, and packed Hastelloy C-276 component shipment. Chemical composition, mechanical, and PMI verification are standard on all project-grade supply.
4.1 — Inspection & QC Protocol
4.2 — EN 10204 / Documentation Requirements
| Certificate | Content | EPC Requirement | When Mandatory |
|---|---|---|---|
| 2.1 / 2.2 | Declaration / non-specific | Not acceptable for critical process supply | Never for critical chemical process equipment supply |
| 3.1 (EN 10204) | Heat-traceable chemical + mechanical test report | Mandatory — all EPC supply | All chemical process and pollution control component supply |
| 3.2 (EN 10204) | 3.1 + TPI countersign | Critical / owner-specified critical items | High-consequence chemical process pressure equipment |
4.3 — Applications by Industry
Flue Gas Desulphurisation (FGD) and Pollution Control
Hastelloy C-276 components for FGD scrubber systems exposed to hot, highly acidic, chloride-bearing flue gas condensate — one of the most demanding combined acid/chloride/temperature environments in industrial equipment, where C-276’s broad-spectrum resistance provides reliable long-term performance where lesser alloys would fail.
Pulp and Paper Bleach Plant Equipment
C-276 tanks, piping, and equipment for chlorine dioxide bleaching stages in pulp and paper manufacturing — leveraging the alloy’s specific, well-documented wet chlorine and hypochlorite resistance advantage discussed in Section 1.2.
Chemical Process “Problem-Solving” Applications
C-276 as the default specification for chemical process equipment exposed to mixed, variable, or incompletely characterised process chemistry — where the specific corrosive challenge does not clearly favour a lower-cost alternative alloy, C-276’s broad resistance profile provides a reliable, if premium-cost, engineering solution.
4.4 — Export Packaging Specification
- Tube and pipe ends capped and bore-protected to prevent contamination and moisture ingress during transit, particularly important given the alloy’s typical use in high-integrity chemical process service
- Heat/lot number stamped or tagged on each item, cross-referenced to the accompanying material test certificate
- Components segregated from carbon steel and other dissimilar materials during packing to avoid surface contamination affecting the alloy’s corrosion performance
- Documentation in a waterproof pocket: EN 10204 3.1/3.2 MTC, chemical composition report, mechanical properties report, PMI report, NDT reports, and packing list with form/size breakdown per item
- ISPM-15 timber or export cartons for international shipment, with country of origin and HS tariff code documentation matched to the nickel alloy product category
Submit your form, size, and quantity to RR Hydraulic for a complete, certified commercial offer.