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Hastelloy C-2000 / (2.4675) / UNS N06200

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Hastelloy C-2000 (UNS N06200), also widely known as Alloy C-2000, is one of the most widely used nickel alloys. The grade shows durability over long periods particularly in sulphuric acid environments. Containing a high proportion of nickel, chromium and molybdenum, Alloy C-2000 also contains around 1.5% copper and around 1.5% cobalt.

Generally chosen where sulphuric acid is present, the material is a nickel alloy preferred because the proportions of the elements it contains are very well balanced. Like many other nickel alloys it can be welded and formed readily. Not especially easy to machine, the material can be found in producers’ stocks in plate, bar, wire, tube and electrode form.​‌​​‌​

Machinability: Among nickel-based alloys it offers good machinability and formability. Because of its high chromium and molybdenum content, however, there are some particular points to observe during machining.

Turning and milling: Cutting tools — it can be machined using carbide inserts or hardened steel tooling. Cutting speed — it can be machined at high cutting speeds, but care should be taken against overheating at excessive speeds. Cooling — using cutting fluids prevents the heating that can occur during machining and extends tool life.​‌​​‌​

Weldability: Hastelloy C-2000 can be welded by the TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) processes. It is important to use suitable shielding gases during welding in order to prevent oxidation. Care should be taken that weld zone temperatures do not become excessively high, as excessive thermal stress in this alloy can lead to loss of corrosion resistance.

Heat treatment: The alloy is generally not heat treated. Post-weld annealing treatments can be carried out, however, and are required for stress relief and to prevent excessive hardening.​‌​​‌​

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What Hastelloy C-2000 Is — and Why the Copper Is There

Hastelloy C-2000 (UNS N06200 / W.Nr. 2.4675 / DIN 17744 name NiCr23Mo16Cu) is a wrought, single-phase FCC nickel-chromium-molybdenum solid-solution alloy: nominally Ni 59 · Cr 23 · Mo 16 · Cu 1.6, Fe 3.0 % max, Co 2.0 % max, carbon held to 0.010 % max and silicon to 0.08 % max. It is non-age-hardening; solid-solution strengthening is the only mechanism available. What separates it from the rest of the C-family is a deliberate copper addition — in C-276 and C-22 copper is a residual capped at 0.5 % max, while in C-2000 it is a specified element at 1.3–1.9 %.​‌​​‌​

Why the copper is there — the centrepiece of this page

In the originator’s own words, the alloy is “unique among the versatile nickel-chromium-molybdenum materials in having a deliberate copper addition… This provides greatly enhanced resistance to sulfuric acid.” The same publisher’s metallurgical guide adds that copper “enhances the resistance of nickel in seawater and reducing acids, especially hydrofluoric.”​‌​​‌​

Here is the engineering problem copper solves. In a Ni-Cr-Mo alloy, chromium and molybdenum pull in opposite directions. Chromium forms the passive film that survives oxidising acids (nitric, hot concentrated sulphuric, ferric- or cupric-contaminated streams). Molybdenum suppresses active dissolution in reducing acids (hydrochloric, dilute sulphuric, hydrofluoric, deaerated service). You cannot raise both without limit: the originator describes C-2000 as sitting near “the gamma phase field boundary” — the metastability limit beyond which second phases precipitate during fabrication and welding. C-276 resolved the conflict in favour of molybdenum and accepted only 16 % Cr. Alloy 22 resolved it in favour of chromium and dropped Mo to 13 %. C-2000 takes 23 Cr AND 16 Mo — the maximum the gamma field will hold — and then uses copper as a third lever to cover the one window where even that combination is weak: mid-concentration sulphuric acid at moderate temperature, where the stream is neither oxidising enough for chromium’s passive film to hold nor reducing enough for molybdenum alone to carry it.

What the copper costs — stated honestly

Honest Positioning in the Family — C-2000 · C-276 · C-22 · Alloy 59

The honest positioning sentence to publish

C-2000 is NOT a general upgrade on C-276 or C-22. It is a narrower, more expensive tool. It wins decisively in sulphuric acid up to ~80 %, in dilute hydrochloric up to ~10 %, and in hydrofluoric acid, and it carries roughly 25 K better crevice resistance than C-276 (CCT 80 °C vs 55 °C). It loses on ASME code temperature (427 °C vs 677 °C — a hard disqualifier above 427 °C), on standards coverage, on availability and on price. Alloy 59 matches its chromium and molybdenum without the copper — and therefore without what the copper buys. C-22 matches its chromium but gives up 3 points of molybdenum. C-276 matches its molybdenum but gives up 7 points of chromium.​‌​​‌​

Standards by Product Form

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ASME Code Acceptance and MAXIMUM CODE TEMPERATURES​‌​​‌​

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NACE MR0175 / ISO 15156 — how it should be worded​‌​​‌​

The originator’s specification table lists NACE MR0175 / ISO 15156 under “Others”. That is the only publisher in which it could be verified, and N06200 could not be located in any retrievable extract of ISO 15156-3 Annex A. So do not publish a bare “NACE compliant” claim; publish this wording instead:
C-2000 is listed by the alloy originator as compliant with NACE MR0175 / ISO 15156. ISO 15156-3 does not grant blanket approval: a nickel alloy is accepted only in a stated metallurgical condition (solution-annealed, with cold-work and hardness limits) and within stated environmental limits (H₂S partial pressure, chloride, pH, elemental sulphur, temperature). Before ordering for sour service, obtain the current ISO 15156-3 Annex A table reference and its environmental limits, and require the mill certificate to state the delivery condition and hardness. Do not accept “NACE compliant” on a certificate without the table reference.

Product Forms With NO Covering Standard — the Commercially Valuable Section​‌​​‌​

C-2000 was commercialised in the late 1990s and its standards coverage never caught up with C-276’s. The gaps below are commercially live, and this is the section your sales engineers should know by heart.

Chemical Composition

Is there an ASTM / EN divergence in composition?

No — element for element the two routes are identical. The German mill table reproduces the ASTM limits exactly, including P 0.025 and S 0.010. Nickel is “Remainder” in ASTM and “Bal.” in the German table; the meaning is the same. The real divergence is not in composition but in the mechanical minima — see the next section. Note also that whether DIN 17744’s own composition limits diverge from ASTM could not be verified directly; the mill table matching ASTM exactly is suggestive, but the standard itself was not read. And published literature is not a composition source: a 2023 peer-reviewed review tabulates C-2000 as “Ni 57, Cr 23, Mo 16” with no copper at all and Fe 1.5. That is wrong on both counts. The composition source is the ASTM table.​‌​​‌​

Mechanical Properties

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Never confuse the three categories: the specification minimum (what you can contractually enforce), material capability (what the metal can do) and the typical mill value (what a real heat delivered). Never let a typical value into a purchase specification or a design calculation.​‌​​‌​

CONFLICT — ASTM and the German route disagree on the minima. Print both.

There are three divergences and all three are commercially live.
1. The yield minimum is thickness-dependent on the German route and flat in ASTM. ASTM says 310 MPa for everything. The German route says 330 MPa for thin sheet and 280 MPa for heavy section. Consequence: a 3 mm sheet at 315 MPa passes ASTM and FAILS the German sheet requirement. A 50 mm plate at 290 MPa FAILS ASTM and passes the German requirement.
2. The German route imposes an UPPER tensile limit (950 or 1000 MPa); ASTM imposes none. A heat at 1020 MPa is acceptable to B575 and rejectable on the VdTÜV route.
3. Never average 310 and 330, and never quote “280–330 MPa” as a range. They are two different acceptance regimes, not the two ends of one band. State the certification route on every certificate.​‌​​‌​

Physical Properties​‌​​‌​

Heat Treatment and Thermal Stability​‌​​‌​

Welding​‌​​‌​

Is a matching filler actually available? Yes.​‌​​‌​

For a young alloy this is a genuine question, and here the answer is clean. Bare rod and wire: ERNiCrMo-17 (AWS A5.14 / SFA-5.14, UNS N06200, EN ISO 18274 S Ni 6200 (NiCr23Mo16Cu2), DIN 2.4698). Covered electrode: ENiCrMo-17 (AWS A5.11 / SFA-5.11, UNS W86200, DIN 2.4699). The originator states plainly that “matching filler metals (i.e. solid wires and coated electrodes) are available“. The commercially important fact is this: at least one European filler maker independent of the alloy originator produces ERNiCrMo-17 MIG wire and TIG rod — so a fabricator is not hostage to a single consumable source. The covered electrode’s ISO 14172 designation could not be verified; EN ISO 18274 was verified for the bare wire only. If a matching filler is genuinely unobtainable for a repair, there is no published qualified alternative: requalify the WPS with the substitute and run the corrosion test the service demands — same acid, same concentration, same temperature — on the actual weldment before it goes in.

As-welded corrosion — the weld is always the faster-corroding element

The originator publishes weld-metal and base-metal rates on the same coupons: 30 % H₂SO₄, 66 °C: weld 0.01 mm/y, base <0.01 mm/y (~2×). 70 % H₂SO₄, 66 °C: weld 0.06 mm/y, base 0.01 mm/y — 6×. 20 % HCl, 38 °C: weld 0.20, base 0.16 (1.25×). 30 % HNO₃, boiling: weld 0.10, base 0.09 (1.1×).
The weld is always the faster-corroding element, by up to 6×. Wherever a weld sees the process fluid, size the corrosion allowance on the WELD rate, not the base-metal rate. A distributor phrase such as “minimal corrosion degradation in welded joints” is directionally true but should not be published without these numbers beside it.​‌​​‌​

Machining

State the caveat plainly: the published data is not specific to C-2000; it is published for the corrosion-resistant Hastelloy C family. Identical figures appear both in the originator’s machining page and in an independently hosted C-22 brochure. Publish them as “starting parameters for solution-annealed corrosion-resistant C-family alloys“, not as C-2000 data.​‌​​‌​

TRAP — a 100× unit-conversion error. The originator’s machining page prints “90 sfm (0.274 m/min)“. 90 sfm is 27.4 m/min. The decimal point is misplaced by two orders. Anyone converting from that page and programming 0.274 m/min will run a 100× slow cut and scrap the job. Publish the corrected conversions above. More generally, the alloy work-hardens faster than austenitic stainless: rigid setup, positive feed, never dwell and never rub — a stalled feed burnishes the surface and the next pass has to cut through a work-hardened skin.​‌​​‌​

Corrosion — Where It Wins and WHERE IT FAILS

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Sulphuric acid — the alloy’s reason to exist​‌​​‌​

Read across: 50 % H₂SO₄, 93 °C — C-2000 0.16 mm/y against C-22 0.77 mm/y. At 79 °C the gap is 0.02 versus 0.40 — a factor of twenty. That single pair of columns is the whole commercial case for the copper. For context, published C-276 rates across 1–96 % run from <0.01 mm/y (10 %, 79 °C) to 13.68 mm/y (70 %, 107 °C) — 13.68 mm/y is the point at which C-276 simply is not a sulphuric acid alloy. But publish the bound as well: 50 % H₂SO₄ at the boil takes C-2000 to 3.35 mm/y — the 50 % advantage evaporates at the boil — and 0.99 mm/y at 80 % / 93 °C is already marginal. “Up to 80 % sulphuric” is a ceiling, not an invitation.​‌​​‌​

Hydrochloric acid — the advantage is real but modest

Read across: 10 % HCl, 66 °C — C-2000 0.65 against C-22 0.98 mm/y. Real, but a 1.5× margin, not the 5–20× of sulphuric. The HCl advantage is genuine but modest. The originator’s claim of superiority “up to 10 %” is honest and correctly bounded: above 10 % the advantage disappears, and even at 10 % the rate is 1.54 mm/y at 79 °C, which is not a usable rate. The alloy class for hot concentrated HCl is the Ni-Mo B family (B-3), not a C alloy.

Hydrofluoric, phosphoric, nitric and organic acids​‌​​‌​

CRITICAL HF CAVEAT — those numbers UNDERSTATE the damage. The originator states it outright: “Hydrofluoric acid is known to cause internal, as well as external, attack of the nickel alloys; these values signify only the amount of external attack encountered during laboratory testing.” The same publisher’s metallurgical guide documents “extremely fine / barely resolvable cracking” in C-2000 exposed to 20 % HF at 79 °C. C-2000 is “the least susceptible to internal attack” of the Ni-Cr-Mo materials tested — but least susceptible is not immune. Weight-loss testing will NOT find this damage; metallographic sectioning will. Do not accept HF service without metallographic verification.​‌​​‌​

Localised corrosion — CPT, CCT, stress-corrosion cracking, seawater

ASTM G28 Method A and B — this one is a PURCHASING HAZARD​‌​​‌​

The originator’s C-2000 bulletin contains no ASTM G28 data at all. This was confirmed on a second, targeted read: the bulletin reports G36 and G48 only. The two third-party figures in circulation differ by more than an order of magnitude: one comes from a competitor distributor with a declared conflict of interest (>500 mpy for G28 B), the other from a transcription that can be shown to mis-align its columns.
Verdict: publish NO ASTM G28 value for C-2000.
Why this matters commercially. ASTM G28 Method A is a routine purchase-order acceptance test for C-276 and alloy 22 — buyers write a maximum into the PO by habit. If that >500 mpy figure is even directionally right, a PO clause copied from a C-276 specification will reject every heat of C-2000 you ever buy. Method B is a mixed-acid (H₂SO₄/HCl/FeCl₃/CuCl₂) test whose chemistry is precisely where a copper-bearing alloy behaves differently from a copper-free one. Before accepting any G28 clause on a C-2000 order, get the mill’s actual G28 result on the specific heat in writing and negotiate the limit against it — do not accept an inherited C-276 limit.

WHERE IT FAILS — the hard disqualifiers​‌​​‌​

OVER-SPECIFIED — where the customer is paying for nothing​‌​​‌​

1. No sulphuric, no HF and no dilute HCl in the stream. The copper is then inert freight. Specify C-276 or C-22: cheaper, broadly stocked, 677 °C code temperature, thicker standards coverage and decades of field history.
2. A chloride-bearing stream at ambient with no acid. A super-duplex (F55) or a 6Mo austenitic will very likely do it at a fraction of the cost.

Frequently Asked Questions​‌​​‌​

When is C-2000 actually worth the money over C-276 or C-22?

Only when three conditions hold together: sulphuric acid, hydrofluoric acid or dilute hydrochloric acid is in the stream, and the design temperature is at or below 427 °C, and crevice geometry is present. Decide on the numbers, not on datasheet adjectives.
The decisive comparison is 50 % H₂SO₄ at 93 °C: C-2000 corrodes at 0.16 mm/y, alloy 22 at 0.77 mm/y — a 4.8× margin; and at 79 °C the margin widens to 20× (0.02 versus 0.40). On a 3 mm corrosion allowance that is the difference between an 18-year wall and a 4-year wall.
The second, quieter case is crevice corrosion: in acidified 6 % FeCl₃ C-2000’s critical crevice temperature is 80 °C against C-276’s 55 °C. Under gaskets, in tubesheet joints and under deposits it is crevice temperature that governs, so 25 K of headroom is real service life in a heat exchanger that C-276 would lose.
Now the disqualifiers, and they are absolute. If the ASME design temperature exceeds 427 °C, C-2000 is off the table — C-276 and C-22 are code-accepted to 677 °C and no corrosion argument overrides a Code limit. If the alloy is for bolting, there is no ASTM bolting specification for N06200. If the customer’s purchase order carries an ASTM G28 acceptance limit copied from a C-276 specification, resolve it before the order: no public consensus G28 value exists for C-2000, and one published figure suggests a C-276 limit would reject every heat.
And if the stream has no sulphuric, no HF and no dilute HCl, C-2000 is pure cost — the copper is the only thing you are buying and the copper is doing nothing.​‌​​‌​

Our drawing says C-276. Can we substitute C-2000, or the reverse?

Not as a drop-in, in either direction, and the failure modes differ.
C-2000 in place of C-276: the immediate blocker is the ASME Section VIII maximum temperature — 427 °C for C-2000 against 677 °C for C-276. If the design temperature is anywhere above 427 °C, the substitution is a code violation regardless of pressure. Second, the filler changes: C-276 joints are welded with ERNiCrMo-4 / ENiCrMo-4, C-2000 with ERNiCrMo-17 / ENiCrMo-17. The WPS must be requalified; the two are not interchangeable, and using the C-276 filler on C-2000 base metal strips the copper out of the weld metal — making the weld the corrosion-limiting element of the joint in exactly the acid the alloy was chosen for, with as-welded rates already up to 6× the base-metal rate in 70 % H₂SO₄. Third, check the P-number on the existing procedure: the originator prints P-No. 43 for N06200 while an independent welding source assigns P-No. 44 to N10276. Those two cannot both be right for the family, and a wrong P-number invalidates the qualification and every weld under it. Read ASME IX Table QW/QB-422 directly before proceeding.
C-276 in place of C-2000: you lose the sulphuric acid performance the alloy was specified for — potentially a factor of 20 at 50 % acid — and you lose 25 K of crevice resistance (CCT 55 versus 80 °C). You gain 250 K of code temperature and a substantially lower price. If the original specification chose C-2000 for a sulphuric duty, this substitution is a service-life decision dressed as a commercial one, and it needs the process engineer’s written sign-off, not procurement’s.​‌​​‌​

We need 12 mm plate, 2 m of 50 mm bar and 200 m of drawn wire in this alloy. What can you actually certify?

The plate and the bar are straightforward; the wire is not — and the difference is a standards gap, not a stock problem.
Plate is covered by ASTM B575 / ASME SB-575: minimum 690 MPa tensile, 310 MPa yield at 0.2 % offset, 45 % elongation in 50.8 mm, solution annealed. The 100 HRB figure printed in B575 is explicitly informational — do not let it into the purchase order as a reject limit. Bar is covered by ASTM B574 / SB-574 at the same three minima. Both certify normally to EN 10204 3.1, with 3.2 available. (Reminder: EN 10204 is a certificate type, not a material standard.)
Drawn wire has NO ASTM specification. It is absent from the alloy originator’s own specification table, and it is a gap across this whole alloy family — the alloy 59 datasheet shows the identical blank. B574 covers rod and bar, B575 covers flat-rolled product, B619 covers welded pipe; none of them covers wire — and at least one well-known wire house cites exactly those standards for wire on its public page, which is citing the wrong standard. What this means practically: wire is sold to the producing mill’s own datasheet; there is no specification minimum to enforce and no third-party acceptance criterion to fall back on in a dispute. Put the acceptance criteria in the purchase order yourself: tensile range and temper, diameter tolerance, cast and helix, surface condition, and the test method for each. Be aware too that wire in this alloy is typically supplied above plate and bar strength levels, because strip and wire anneal practice differs from plate practice: one strip producer anneals at 1065 °C against the 1149 °C used for plate, and reports a typical annealed tensile of 860 MPa against 758 MPa for plate. Do not size a wire component on plate data.​‌​​‌​

Common Datasheet Errors and Traps

1. W.Nr. 2.4675 is the BASE METAL. 2.4698 and 2.4699 are FILLER metals. The originator’s own alloy-portfolio page lists “DIN 2.4699” against C-2000 — that is the covered electrode (EL-NiCr23Mo16Cu), not the alloy. 2.4698 is the bare wire (SG-NiCr23Mo16Cu). The base metal is 2.4675, per DIN 17744. Ordering plate to “2.4699” orders welding consumable.
2. UNS N06200 is the base metal AND the bare wire. W86200 is the COVERED ELECTRODE. The originator lists both against the alloy; distributors routinely publish “UNS W86200” as the plate grade. It is not.
3. The ASME Section VIII ceiling is 427 °C, not 677 °C. Every other alloy in the C-family (C-276, C-22) is code-accepted to 677 °C. C-2000 is not. This is the single most consequential fact on the page and the one most often omitted from distributor datasheets.
4. ASME 427 °C and VdTÜV 450 °C are DIFFERENT ceilings on DIFFERENT routes. Never quote 450 °C on an ASME job.
5. Density is 8.50 g/cm³, not 8.7. A modelled database publishes 8.7; four sources including the originator publish 8.50. The 2.4 % error mis-invoices tonnage — 145 kg on a 6-tonne plate order.
6. The melting range is 1328–1358 °C; not 1399 °C and not 1450–1500 °C. A wire house publishes 1399 °C and a modelled database publishes 1450–1500 °C. Three sources including the originator publish 1328–1358 °C. Modelled databases are not measurement sources — do not cite one for this alloy at all.
7. The modulus is disputed: 207 GPa (originator) versus 218 GPa (German mill). Print both. A 5 % modulus error propagates into every deflection and bolt-preload calculation.
8. The specification minimum yield is 310 MPa (ASTM); typical mill yield is 345–359 MPa. A designer sizing on 359 MPa is sizing on a number the mill owes nothing for. Never let a typical value into a design or a purchase order.
9. The ASTM and German mechanical minima genuinely differ, and the German route has an UPPER tensile limit. ASTM: 310 MPa yield, 690 MPa tensile minimum, no ceiling. German: 330 MPa yield for sheet ≤4 mm, 280 MPa for >4–65 mm, with tensile capped at 1000/950 MPa. A heat can pass one and fail the other. State the certification route on every certificate.
10. The 100 HRB in ASTM B575 is INFORMATIONAL, not an acceptance limit. Do not write it into a purchase order; do not accept a rejection based on it.
11. P-No. 43 versus P-No. 44 is unresolved. The originator prints P-43 for N06200; an independent source assigns P-44 to N10276 in the same family. Read ASME IX QW/QB-422 before writing the WPS. A wrong P-number invalidates the procedure and every weld under it.
12. “Green Death” CPT is published at 80, 100, 110 and 120 °C by four sources — two of them the same publisher in two different documents. Print the disagreement. Do not average. Do not pick the highest.
13. Do not publish a Code Case number. One distributor claims “Code Case 2337” for the filler with no corroboration. By contrast the originator’s C-22 table explicitly cites Code Case 2226-2 and Case N-621-1, while the C-2000 table cites none.
14. Do not publish a magnetic permeability (µr) figure. The structure is FCC and non-ferromagnetic in the annealed condition, but no measured µr appears in any source checked. State the structure; give no number.
15. Do not publish a PREN without the formula. The same competitor table prints two different PREN columns for the same alloys (47 and 76 for C-2000). PREN formulae are not standardised across publishers, and PREN is in any case a stainless-steel index. Use the measured CPT/CCT for decisions.
16. Every corrosion number on this page is reagent-grade laboratory data. The originator’s own caveat is: “All tests were performed in reagent grade acids under laboratory conditions; field tests are encouraged prior to industrial use.” Publish the caveat with the tables, not in a footnote — real process streams carry oxidising contaminants (Fe³⁺, Cu²⁺, dissolved oxygen), halides and velocity, all of which move these numbers.​‌​​‌​

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