A contractor near Hamburg orders Hastelloy C2000 plate, 6 mm, for a 40% sulfuric acid tank, 20-year design life. The question on the RFQ is not what alloy to use - that is already settled - but whether 6 mm leaves enough metal after uniform corrosion. The answer is a simple multiplication, yet most buyers stop at the Haynes corrosion-rate table and never turn it into a wall-thickness number. This page shows the arithmetic.
The product in one table
Table 1 - Hastelloy C2000 plate specification row (ASTM B575, solution-annealed)
|
Item |
Value |
|
UNS / W.Nr. |
N06200 / 2.4675 |
|
Chemistry |
Ni bal, Cr 22.0–24.0, Mo 15.0–17.0, Cu 1.3–1.9, Fe ≤3.0, Co ≤2.0, Mn ≤0.50, Si ≤0.08, C ≤0.010, S ≤0.010 |
|
Mechanical (plate, room temp) |
690 MPa tensile min / 310 MPa yield min / 45% elongation min |
|
Density |
8.50 g/cm³ |
|
Melting range |
1,370–1,410 °C |
|
Heat treatment |
Solution anneal 1,050–1,150 °C, rapid cool |
|
PREN |
~76 (Cr + 3.3Mo + 16N, N≈0) |
|
Related standards |
B575 plate/sheet/strip; B619 welded pipe; B622 seamless pipe; B366 fittings |
The chemistry is the product. The 22–24% chromium handles oxidizing acids, the 15–17% molybdenum handles reducing chlorides, and the 1.3–1.9% copper tilts the alloy toward sulfuric acid resistance. It is the Cu addition that separates C2000 from C276 on a datasheet.
Corrosion-rate data: the starting point
Haynes International publishes 24-hour immersion data for solution-annealed C2000. For sulfuric acid design, the relevant rows are:
Table 2 - Hastelloy C2000 plate corrosion rate in sulfuric acid (mm/year, solution-annealed)
|
H₂SO₄ concentration |
24 °C |
50 °C |
75 °C |
100 °C |
Boiling |
|
10% |
<0.025 |
<0.025 |
<0.025 |
<0.025 |
0.09 |
|
20% |
<0.025 |
<0.025 |
<0.025 |
0.03 |
0.18 |
|
40% |
<0.025 |
<0.025 |
<0.025 |
0.05 |
0.42 |
|
60% |
<0.025 |
<0.025 |
0.02 |
0.16 |
1.13 |
|
80% |
<0.025 |
<0.025 |
0.07 |
0.37 |
0.91 |
|
96% |
<0.025 |
<0.025 |
<0.025 |
0.05 |
0.19 |
These are laboratory values on clean samples. Real tanks see weld heat tint, deposits, start-up upsets and occasional chloride carry-over. A field factor of 2–3× is conservative for design.
The corrosion-allowance formula
For uniform corrosion, the required corrosion allowance is:
Corrosion allowance (mm) = corrosion rate (mm/y) × design life (y) × field factor
ASME VIII-1 does not set the field factor; it is a project decision. Common practice for non-removable process equipment is field factor = 2.0 and design life = 20 years. If the component is inspectable and replaceable, a factor of 1.5 may be accepted.
Table 3 - Corrosion allowance calculation example: 40% H₂SO₄, 75 °C, 20-year life
|
Input |
Value |
|
Service |
40% H₂SO₄, 75 °C |
|
C2000 plate lab rate |
<0.025 mm/y (use 0.025) |
|
Field factor |
2.0 |
|
Design life |
20 y |
|
Required corrosion allowance |
0.025 × 20 × 2.0 = 1.0 mm |
|
Structural minimum (project) |
3.0 mm |
|
Specified nominal thickness |
6.0 mm |
|
Remaining wall after 20 y |
6.0 − 1.0 = 5.0 mm |
For this case, 6 mm is generous. But if the temperature rises to boiling 40% acid, the rate jumps to 0.42 mm/y and the required allowance becomes 16.8 mm before the field factor. That is why the same acid at two different temperatures can move the plate thickness by more than 10 mm.
C2000 vs C276 vs C22 plate: cost per mm lost
The corrosion allowance is only half the decision. The other half is what each millimetre of lost metal costs, because the alloys do not corrode at the same rate and do not cost the same.
Table 4 - Plate alloy comparison for sulfuric acid service (indicative)
|
Alloy |
UNS |
H₂SO₄ 40%, 75 °C rate (mm/y) |
20-y allowance, F=2 (mm) |
Relative plate price |
Cost per mm lost (indexed) |
|
Hastelloy C2000 |
N06200 |
0.025 |
1.0 |
1.25 |
1.0 |
|
Hastelloy C276 |
N10276 |
0.08 |
3.2 |
1.20 |
3.0 |
|
Hastelloy C22 |
N06022 |
0.06 |
2.4 |
1.30 |
2.6 |
|
904L |
N08904 |
0.50 |
20.0 |
0.35 |
Not viable |
|
316L |
S31603 |
>2.0 |
>80 |
0.10 |
Not viable |
The table is simplified - actual rates vary with impurities, flow and weld condition - but the message is clear: for hot, reducing sulfuric acid, C2000's low corrosion rate can justify its higher base price because the required corrosion allowance is smaller. For oxidizing chloride service, the comparison shifts toward C22. For pure reducing HCl, C276 often wins.
Hydrochloric acid boundary
C2000 also handles HCl better than C276 at low concentrations, but the rate rises fast with temperature:
Table 5 - Hastelloy C2000 plate corrosion rate in hydrochloric acid (mm/year)
|
HCl concentration |
24 °C |
50 °C |
Boiling |
|
1% |
<0.025 |
<0.025 |
0.05 |
|
5% |
<0.025 |
0.05 |
0.13 |
|
10% |
<0.025 |
0.08 |
0.25 |
|
20% |
0.05 |
0.13 |
0.51 |
For boiling 10% HCl, a 20-year allowance at F=2 would be 10 mm. That is why HCl service above roughly 50 °C usually pushes the design toward C-22 or B-3 rather than C2000, despite C2000's better sulfuric-acid performance.
Specs, sizes and price band
C2000 plate is supplied solution-annealed and pickled, typically 3–50 mm thick in widths 1,000/1,200/1,500/2,000 mm and lengths to 6,000 mm. Cold-rolled sheet runs 0.5–6 mm. Tolerances follow ASTM B575 / ASTM A480. Indicative FOB China pricing is USD 18–32/kg depending on thickness and order quantity. The price tracks the nickel line plus the molybdenum and cobalt surcharges.
FAQ
Q: What is the difference between Hastelloy C2000 and C276 plate?
A: C2000 adds 1.3–1.9% copper to the Ni-Cr-Mo base, which improves resistance to sulfuric acid and some mixed acids. C276 carries more molybdenum (15–17% vs C2000's 15–17% similar band) and tungsten, giving better resistance to hot hydrochloric acid. For sulfuric acid, C2000 usually wins; for HCl, C276 is often the better spend.
Q: Can I use the Haynes corrosion-rate numbers directly in ASME VIII-1?
A: No. The published numbers are 24-hour laboratory immersion values. Design codes require a corrosion allowance that accounts for field factors, weld effects, start-up upsets and inspection intervals. Multiply the lab rate by a project-defined factor, typically 1.5–3.0.
Q: Is Hastelloy C2000 plate weldable?
A: Yes, in the solution-annealed condition using matching ERNiCrMo-17 or ERNiCrMo-4 filler, depending on whether you want the weld to match C2000 or lean toward C276 chemistry. Keep interpass temperature below 150 °C and use argon backing gas on root passes.
Q: What should I verify on the MTR for C2000 plate?
A: Verify carbon ≤0.010%, copper 1.3–1.9%, molybdenum 15.0–17.0%, and that the plate is supplied in the solution-annealed condition. A G28A intergranular corrosion test result is often added for critical acid service.
Q: When is C2000 plate not the right choice?
A: For strong oxidizing chlorides such as wet chlorine or ferric chloride, C22 or C276 outperform C2000. For long-term service above roughly 650 °C, solid-solution nickel grades such as 600 or 800H are better. For pure caustic, Nickel 201 is the cheaper correct choice.
How To Cooperate With Us?
end your acid concentration, temperature, design life and minimum structural thickness to market@htpipe.com. We supply Hastelloy C2000 plate to ASTM B575, we will calculate the corrosion allowance from the published rate data, and we will tell you plainly if C276 or C22 plate is the lower life-cycle-cost choice for your acid.
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