Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Monel 400 vs Hastelloy C-276 - Ni-Cu vs Ni-Cr-Mo Selection Matrix
Monel 400 (UNS N04400, ASTM B164) is a nickel-copper alloy at 63 to 70 percent Ni and 28 to 34 percent Cu, with no chromium and no molybdenum. Hastelloy C-276 (UNS N10276, ASTM B574) is a nickel-chromium-molybdenum-tungsten alloy at 57 percent Ni with 14.5 to 16.5 Cr, 15.0 to 17.0 Mo and 3.0 to 4.5 W. The Monel 400 vs Hastelloy C-276 selection is driven by the presence or absence of chromium in the passive film. Monel 400 is specified where chromium is attacked: HF at every concentration, anhydrous HF, ambient flowing seawater, and dilute reducing acids. Hastelloy C-276 is specified where copper is attacked: mixed acid, hot oxidising acid, wet chlorine and hypochlorite, and the broadest pH band in one specification. Monel® is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals. Hastelloy is a registered trademark of Haynes International. Numbers cited are from ASTM B164, ASTM B574, ASTM F468, NACE MR0175 / ISO 15156-3 and API RP 751.
Selection Summary: Which Alloy for Which Service
The monel 400 vs hastelloy c276 decision reduces to one chemistry fact. Monel 400 has zero chromium, so it survives where Cr is attacked (HF, ambient flowing seawater, hot NaOH). Hastelloy C-276 carries 15 to 17 percent Mo on a Cr-Ni base, so it survives where Cu is attacked (mixed acid, hot oxidising acid, wet chlorine). The alloys overlap only at sour bolting and ambient marine flanges.
| Service environment | Specified alloy | Reason |
|---|---|---|
| HF acid, anhydrous HF | Monel 400 (mandatory) | API RP 751; Cr is attacked by HF. |
| Flowing seawater, splash, tidal | Monel 400 (preferred) | Ni-Cu film holds; C-276 over-specified. |
| NaOH caustic, hot | Monel 400 | Industry baseline for hot caustic. |
| Mixed acid (HCl + oxidiser) | Hastelloy C-276 (mandatory) | Mo + W spans the reducing-to-oxidising band. |
| Hot HNO3, hot dilute H2SO4 | Hastelloy C-276 | Cu2+ accelerates Monel 400 dissolution. |
| Wet chlorine, hypochlorite, ClO2 | Hastelloy C-276 | N10276 designed for pulp bleach and FGD. |
| Sour service H2S, NACE MR0175 | Both qualified | N04400 at 35 HRC; N10276 at 40 HRC. |
Chemistry Comparison: N04400 vs N10276
Monel 400 is a single-phase FCC nickel-copper solid solution. Hastelloy C-276 is a single-phase FCC nickel-chromium-molybdenum solid solution with tungsten. Chromium and molybdenum drive the C-276 passive film; copper drives the Monel 400 film.
| Element | Monel 400 (N04400) | Hastelloy C-276 (N10276) |
|---|---|---|
| Nickel Ni, % | 63.0 to 70.0 | balance, nominal 57 |
| Copper Cu, % | 28.0 to 34.0 | 0.50 max |
| Chromium Cr, % | none | 14.5 to 16.5 |
| Molybdenum Mo, % | none | 15.0 to 17.0 |
| Tungsten W, % | none | 3.0 to 4.5 |
| Iron Fe, % | 2.5 max | 4.0 to 7.0 |
| Cobalt Co, % | residual | 2.5 max |
| Manganese Mn, max % | 2.00 | 1.00 |
| Silicon Si, max % | 0.50 | 0.08 |
| Carbon C, max % | 0.30 | 0.010 |
| P / S max % | 0.024 / 0.024 | 0.04 / 0.03 |
Source: ASTM B164 for Monel 400; ASTM B574 / B575 for C-276. Trace-element rules on the chemical composition page.
Mechanical Properties Comparison
Both alloys ship solution-annealed for corrosion service. C-276 carries a higher tensile minimum from 15 to 17 Mo plus W solid-solution strengthening. Monel 400 catches up only in the cold-worked condition.
| Property (annealed) | Monel 400 | Hastelloy C-276 |
|---|---|---|
| Tensile strength min, ksi (MPa) | 70 (480) | 100 (690) |
| Yield strength 0.2% offset min, ksi (MPa) | 25 (170) | 41 (283) |
| Elongation in 2 in. min, % | 35 | 40 |
| Hardness max | typically 75 to 95 HRB | 100 HRB max annealed |
| Cold-worked yield, ksi (MPa) typical | 85 (585) | up to 130 (895) |
| Density, g/cm³ | 8.80 | 8.89 |
| Elastic modulus, GPa (Msi) | 179 (26) | 205 (29.8) |
| Max service temperature, deg C continuous | 540 (then K-500 territory) | 1090 for short cycles, 677 for long-term creep |
Sources: ASTM B164 Table 1 (Monel 400 annealed rod); ASTM B574 / B575 for C-276. See mechanical properties.
Corrosion Behaviour by Environment
Monel 400 holds in reducing service and HF; C-276 holds in oxidising and mixed-acid service; both qualify in sour and seawater.
| Environment | Monel 400 | Hastelloy C-276 |
|---|---|---|
| HF acid, anhydrous HF | best | poor (Cr attacked) |
| Seawater, flowing, ambient | best | best (over-spec) |
| Seawater, stagnant, crevice | good | best |
| NaOH caustic, hot | best | good (Cr leaches) |
| Dilute HCl, deaerated | good | best |
| HCl + oxidiser, pickling | poor | best |
| Hot HNO3, hot oxidising acid | poor | best |
| Wet chlorine, hypochlorite, ClO2 | poor | best |
| Hot FeCl3, CuCl2 (ASTM G48) | poor | best |
| Sour service H2S, NACE MR0175 | qualified, 35 HRC | qualified, 40 HRC CW |
| Anhydrous ammonia | good | good |
Detail on corrosion resistance, HF acid resistance, seawater corrosion and NACE MR0175.
Cost Ratio: C-276 is 2 to 3 Times Monel 400 by Weight
Mill price is a weighted average of LME and ferro-alloy feeds. C-276 is set by LME nickel at 57 percent, LME molybdenum at 15 to 17 percent, ferro-chromium and ferro-tungsten. Monel 400 is set by LME nickel at 63 to 70 percent and LME copper at 28 to 34 percent. Mo and W trade at a multiple of copper. At mid-cycle LME, C-276 to Monel 400 sits at 2 to 3 by weight; in tight Mo cycles the ratio runs to 3.5. Bar-to-bolt conversion is alloy-independent. LME-to-quote bridge on the pricing page.
Where Hastelloy C-276 is the Specified Alloy
Mixed-acid service. Refinery acid-regeneration, FGD scrubbers, sulphuric-acid alkylation, and HCl-plus-oxidiser pickling load alloys with both reducing and oxidising agents. Mo plus W in C-276 keeps the passive film stable. Monel 400 fails on the oxidising side as Cu2+ accelerates dissolution.
Hot oxidising acids. Hot HNO3, hot dilute H2SO4 with aeration, and hot ferric chloride strip the Ni-Cu film on Monel 400. C-276 holds at 16 percent FeCl3 boiling per ASTM G28 and at 65 percent HNO3 boiling.
Wet chlorine, hypochlorite, ClO2 bleach. Pulp bleach, chlor-alkali cell rooms, and ClO2 generation specify C-276 as baseline. Monel 400 corrodes in oxidising chloride.
Broadest pH band. C-276 holds from pH 1 (HCl) through pH 14 (NaOH) at moderate temperature in a single specification. The trade-off is the cost premium.
Where Monel 400 is the Specified Alloy
Hydrofluoric acid. HF dissolves chromium-rich oxides into volatile chromium fluorides that strip the alloy. C-276 carries 14.5 to 16.5 Cr and is excluded by API RP 751 from HF alkylation primary wetting. Monel 400 has no Cr; the Ni-Cu film is stable across 0 to 99 percent HF and into anhydrous storage. This is the single largest monel vs hastelloy service for which Monel 400 is the only correct answer.
Ambient flowing seawater. Both alloys survive seawater but C-276 is over-specified. Monel 400 shafting, valve trim, propeller hubs, and brackish tubing carry a 60-year service record per Nickel Institute datasets. The C-276 premium is unjustified unless seawater carries oxidising biocide or hot chloride.
Hot caustic NaOH. Monel 400 is the alloy of record for hot NaOH evaporators above 50 percent. C-276 leaches chromium in hot caustic and is rejected for caustic service.
Sour bolting at moderate temperature. Both qualify under NACE MR0175 (N04400 at 35 HRC, N10276 at 40 HRC cold-worked). Monel 400 bolts come in at one-third the price of C-276 bolts and cover the same H2S envelope below 175 degrees Celsius and 50000 ppm chloride.
Machinability and Weldability
Machinability. Both alloys work-harden. Monel 400 needs carbide at 30 to 50 m/min; the free-machining Monel R-405 (N04405) at 0.025 to 0.060 S relaxes the constraint. C-276 is harder on tools from the 15 to 17 Mo; carbide at 15 to 25 m/min with positive rake and high-pressure coolant is standard. See machinability.
Weldability. Monel 400 welds without PWHT to 38 mm with ENiCu-7 or ERNiCu-7 per AWS A5.11 / A5.14. C-276 welds with ERNiCrMo-4 per AWS A5.14, autogenously for thin tube. Dissimilar Monel 400 to C-276 joints use ERNiCrMo-3 (Inconel 625 filler); the joint inherits the lower corrosion ceiling.
Standards Stack Cross-Reference
| Product form | Monel 400 (N04400) | Hastelloy C-276 (N10276) |
|---|---|---|
| Plate, sheet | ASTM B127 | ASTM B575 |
| Rod, bar | ASTM B164 | ASTM B574 |
| Seamless pipe / tube | ASTM B165 | ASTM B622 |
| Condenser tube | ASTM B163 | ASTM B626 |
| Forgings, flanges | ASTM B564 | ASTM B564 |
| Bolts | ASTM F468 | ASTM F468 |
| Nuts | ASTM F467 | ASTM F467 |
| DIN designation | 2.4360 NiCu30Fe | 2.4819 NiMo16Cr15W |
| Sour service | NACE MR0175, 35 HRC | NACE MR0175, 40 HRC CW |
| HF primary wetting | per API RP 751 | excluded |
Applications by Industry
| Industry / service | Monel 400 landing | Hastelloy C-276 landing |
|---|---|---|
| Refinery HF alkylation | internals, trim, bolting per API RP 751 | excluded from HF wetting |
| Sour-gas wellhead bolting | flange bolting, 35 HRC | high-chloride wellhead, 40 HRC |
| Seawater pumps, valves, shafts | baseline alloy | where biocide or hot chloride present |
| Hot caustic NaOH evaporators | baseline above 50 percent | not specified |
| Pulp bleach (ClO2, hypochlorite) | not specified | baseline alloy |
| FGD scrubber wetted internals | not specified | baseline alloy |
| Pickling lines (HCl + oxidiser) | not specified | baseline alloy |
| Brackish heat exchanger tubing | per ASTM B163 | per ASTM B622 / B626 in hot chloride |
Frequently Asked Questions
Why is Monel 400 specified for HF acid where C-276 is not? HF dissolves chromium-rich oxides into volatile chromium fluorides and forms mixed Cr-F-Cl scale that strips the alloy. C-276 carries 14.5 to 16.5 Cr; Monel 400 has no Cr. API RP 751 names Monel 400 (UNS N04400) as the standard HF alkylation alloy.
Where is C-276 the specified alloy over Monel 400? Mixed acid with simultaneous oxidising and reducing agents, hot oxidising acids (hot HNO3, hot dilute H2SO4), wet chlorine and hypochlorite, hot ferric chloride, ClO2 pulp bleach, and the broadest pH band. Monel 400 attacks rapidly in oxidising acid because Cu2+ strips the film.
What is the cost ratio of C-276 to Monel 400? Approximately 2 to 3 times Monel 400 by weight at mid-cycle LME. C-276 is set by LME nickel plus LME molybdenum (15 to 17 percent) plus ferro-tungsten; Monel 400 is set by LME nickel plus LME copper. Mo and W trade at a multiple of copper.
Are both alloys qualified for sour service? Yes. Both UNS N04400 and UNS N10276 are listed in NACE MR0175 / ISO 15156-3. Monel 400 caps at 35 HRC; C-276 caps at 40 HRC for cold-worked product. Selection is driven by chloride loading and temperature.
Can Monel 400 and C-276 be welded to each other? Yes. Standard dissimilar filler is AWS A5.14 ERNiCrMo-3 (Inconel 625) or ERNiCrMo-4. GTAW with argon shielding and controlled heat input. PWHT is not required on either side.
Related Pages
Reference: chemical composition, corrosion resistance, HF acid resistance, HF alkylation, nickel-copper alloy, vs stainless steel, vs Monel K-500, NACE MR0175. Product forms: bolts, stud bolts, round bar, plate, tubing, seamless pipe, flanges. Pricing: Monel 400 pricing.
Request a Quote
For a Monel 400 vs Hastelloy C-276 selection review, send operating temperature, fluid composition (HF, H2S partial pressure, chloride ppm, oxidising agents), product form and quantity to info@torqbolt.com or WhatsApp +91-22-66157017. TorqBolt QA-QC returns the alloy-selection memo, EN 10204 cert type, mill source and Ex-Mumbai price within one working day. Domestic India 3 to 7 working days; export through JNPT.
References
ASTM B127, B164, B564, B165, F467, F468 (Monel 400). ASTM B574, B575, B622, B626 (C-276). NACE MR0175 / ISO 15156-3 (Part 3, CRAs). API RP 751 (HF alkylation safe operation). Nickel Institute publications on Monel 400. Haynes International handbook for HASTELLOY C-276. AWS A5.11 and A5.14.
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