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Nickel 201 alloy is a pure nickel alloy with good performance and wide application. It has excellent acid resistance, salt resistance and alkali resistance. Nickel 201 has excellent caustic resistance and can even resist molten caustic corrosion.
Nickel 201 can maintain good thermal conductivity, electrical conductivity and mechanical properties. Because nickel alloy 201 has good strength and plasticity, it is widely used in industry. In addition to its value, pure nickel can be used as corrosion-resistant structural
materials and functional materials due to its good properties. For example, according to the ASME Boiler and Pressure Vessel Code, Nickel 201 is approved for the construction of pressure vessels with working temperatures up to 1250°F.
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| Grade | UNS | C≤ | Mn≤ | Si≤ | S≤ | Cu≤ | Fe≤ | Ni(min) |
| Ni201 | N02201 | 0.02 | 0.35 | 0.35 | 0.01 | 0.25 | 0.40 | 99.0 |
Density | 8.88 g/cm3 |
Specific Heat | 456 J/Kg*K |
Intrinsic Resistance | 9.2 μΩ*cm |
Thermal Conductivity | 72.7 W/m*K |
Longitudinal Elastic Modulus | 21.1x104 MPa |
Melting Point | 1433-1444℃ |
Form | Tensile Strength | Yield Strength (0.2% Offset) | Elongation in 2 in. (51 mm), % | Hardness | |||
Brinell | Rockwell B | ||||||
ksi | MPa | ksi | MPa | ||||
Rod and Bar | |||||||
Hot-Finished and Hot-Finished, Annealed Cold-Drawn Cold-Drawn, Annealed | 50-60 60-100 50-60 | 345-415 415-690 345-415 | 10-25 35-90 10-25 | 70-170 240-620 70-170 | 60-40 35-10 60-40 | 75-100 125-200 75-100 | – – – |
Plate | |||||||
Hot-Rolled Hot-Rolled, Annealed | 50-70 50-70 | 345-485 345-485 | 12-35 12-35 | 83-240 83-240 | 60-35 60-40 | – – | – – |
Tube and Pipe (Seamless) | |||||||
Cold-Drawn, Annealed Stress-Relieved | 50-70 60-105 | 345-485 415-725 | 10-28 30-85 | 70-195 205-585 | 60-40 35-15 | – – | 62 max. 70-95 |
STANDARD | WERKSTOFF.NR. | UNS | JIS | BS | GOST | EN |
Ni201 | 2.4061/2.4068 | N02201 | NW 2201 | NA 12 | HП-2 | LC-Ni 99 |
Nickel 201's defining feature is its ultra-low carbon content (0.02% max, versus 0.15% max for Nickel 200) — this single difference is what lets it hold its ductility and corrosion resistance in continuous service up to 1,250°F (677°C), where standard Nickel 200 cannot be reliably used.
Above roughly 600°F, the carbon dissolved in Nickel 200 can precipitate as graphite at the grain boundaries during long-term exposure. This graphitization embrittles the material and can reduce its corrosion resistance right at the grain boundary. Nickel 201's 0.02% carbon ceiling keeps carbon low enough that this precipitation does not become a practical problem, which is why the ASME Boiler and Pressure Vessel Code approves N02201 for pressure vessel construction at temperatures up to 1,250°F, while Nickel 200 is generally restricted to service below 600°F.
Other characteristics that follow from its near-100% nickel composition:
Outstanding alkali resistance — resists caustic soda and caustic potash at all concentrations, including molten (fused) caustic, better than almost any other commercial engineering alloy.
Ferromagnetic with useful magnetostriction — Nickel 201 remains magnetic well above room temperature (Curie point ≈ 354°C / 670°F), which is why it is still specified for magnetostrictive transducers and certain electronic/electrical components.
High thermal and electrical conductivity — useful in heat-transfer equipment and electrical/electronic parts where pure nickel's conductivity is an advantage over more heavily alloyed grades.
Excellent formability — its low carbon content and fine, stable grain structure give Nickel 201 better deep-drawing performance than Nickel 200, which is why ultra-thin drawn or stamped nickel components favor 201 over 200.
Reliable weldability — welds without the risk of carbon-related embrittlement in the heat-affected zone that can affect higher-carbon Nickel 200 in elevated-temperature service; ERNi-1 (AWS A5.14) is the standard matching filler metal.
Resistant to dry chlorine and fluorine gas at elevated temperature — an additional reason it is specified for halogen-handling equipment alongside its caustic service.
Not intended for oxidizing acid service — like all commercially pure nickel grades, Nickel 201 is not the right choice for nitric acid or other strongly oxidizing acidic media; it belongs to the "primarily for caustic/reducing service" family of nickel alloys rather than the acid-resistant nickel-molybdenum or nickel-chromium families.
Product | Standard | Show |
Nickel 201 Pipe Smls | ASTM B161, ASTM B163 |  |
Nickel 201 Pipe Welded | ASTM BB474, ASTM B464 |  |
Nickel 201 Tube Smls | ASTM BB161, ASTM B163 |  |
Nickel 201 Sheet/Plate | ASTM B162 |  |
Nickel 201 Bar | ASTM B160 |  |
Nickel 201 Fitting | ASTM B366 |  |
Nickel 201 Forging | ASTM B564 |  |
Caustic evaporators
Electronic components
Reactors and vessels in which fluorine is generated and reacted with hydrocarbons
Heat exchangers
Stamped or etched fabrications
Nickel 201 is the standard material for high-temperature and high-concentration caustic handling because it resists caustic soda and caustic potash at every concentration — including molten caustic — without the graphitization risk that limits Nickel 200, and its non-contaminating surface makes it a trusted choice wherever product purity matters as much as corrosion resistance.
Chemical processing applications:
Caustic soda (NaOH) and caustic potash (KOH) production — evaporators, piping, valves, and pumps in both diaphragm-cell and ion-membrane chlor-alkali processes, including duty on concentrated and molten/fused caustic streams where the working temperature would graphitize Nickel 200.
Synthetic (rayon) fiber manufacture — spinning baths and associated equipment that run continuously in hot caustic solution.
Fluorine and anhydrous hydrofluoric acid handling — reactors and piping in duty that generates or reacts fluorine with hydrocarbons.
Electroplating — anodes, anode baskets, tanks, and bus bars for nickel-plating baths, where Nickel 201's own composition doesn't introduce unwanted alloying elements into the bath.
Organic chemical synthesis reactors — vessels and internals where trace metallic contamination from a more heavily alloyed material could interfere with the reaction or product purity.
Food and beverage processing applications:
Evaporators and concentration equipment — Nickel 201's caustic resistance is what makes it suitable for equipment that undergoes frequent caustic clean-in-place (CIP) cycles, a routine part of dairy and food-processing sanitation.
Dairy processing equipment — evaporators and process vessels exposed to repeated hot caustic cleaning without the risk of carbon-related surface degradation over the equipment's service life.
Vegetable oil hydrogenation — reactor vessels and internals in hydrogenation processes that traditionally use nickel-based equipment.
Salt and brine evaporation systems — equipment handling concentrated brine solutions in food-grade salt production.
Stamped and etched fabrications for food-contact components — Nickel 201's superior deep-drawing performance (see Block 1) makes it the practical choice when a food-contact part needs to be formed from thin sheet.
For food-contact equipment, always confirm the specific finished component's compliance with the relevant food-safety regulations (FDA, EU, or the applicable local authority) — material chemistry alone does not constitute a food-contact certification.
The main difference between the two is the carbon content.
N02200: C% not more than 0.15; N02201: C% not more than 0.02.
Nickel200 has a relatively high carbon content and may be graphitized under high temperature conditions, which may impair product performance. Therefore, Nickel 200 is usually limited to use in environments below 600°F, while Nickel 201 is relatively more resistant to high temperatures and is approved for service at 1250°F.
Generally speaking, there is little difference in the corrosion resistance of the two, and Nickel201 is more resistant to intergranular corrosion during welding.
In terms of deep stamping performance, Nickel201 performs significantly better, so the ultra-thin nickel box used for electronic components and electronic products is made of Nickel201 and Nickel205 with higher standards.
Note: German VDM and other manufacturers control the carbon content to produce materials that meet the dual standards of 200 and 201 under general conditions, which are suitable for a wider range of application environments.
Choose Nickel 201 for caustic soda/potash service — especially high-concentration, high-temperature, or molten caustic — and for duty where alloy purity matters. Choose Monel 400 for hydrofluoric acid, seawater/marine service, and applications needing higher as-supplied strength. The two alloys are complementary rather than competing: both resist caustic well, but each has a corrosive environment where it is clearly the better choice.
| Dimension | Nickel 201 (UNS N02201) | Monel 400 (UNS N04400) |
|---|---|---|
| Composition | Ni ≥ 99.0%, C ≤ 0.02% | Ni ≥ 63%, Cu 28–34%, Fe ≤ 2.5% |
| Tensile Strength (annealed) | ~345–415 MPa (50–60 ksi) | ~480–585 MPa (70–85 ksi) |
| Yield Strength (annealed, 0.2%) | ~70–170 MPa (10–25 ksi) | ~190–345 MPa (28–50 ksi) |
| Max Continuous Service Temp | Up to 677°C (1,250°F) — ASME BPVC approved for pressure vessels | ~480°C (900°F) in air; strength and oxidation resistance fall off above this |
| Caustic Soda/Potash Resistance | Outstanding at all concentrations, including molten/fused caustic | Very good across the full concentration range, but not rated for molten caustic |
| Hydrofluoric Acid Resistance | Not a primary use case | Outstanding — one of the few practical materials for HF acid and fluorine gas service |
| Seawater / Marine Resistance | Not typically specified | Excellent — resists chloride pitting and stress corrosion cracking |
| Oxidizing Acid Resistance | Poor (not intended for nitric acid or similar oxidizing acids) | Poor to moderate; loses HF resistance if oxidizing conditions or air are present |
| Magnetic Property | Ferromagnetic at room temperature (Curie point ≈ 354°C / 670°F) | Near-ambient Curie point (21–49°C); effectively non-magnetic once warm, but not reliably non-magnetic at room temperature |
| Machinability | Soft and ductile; more prone to galling/built-up edge | Good machinability; a recognized advantage of the alloy |
| Weldability | Excellent; matching filler ERNi-1 (AWS A5.14) | Good; matching filler ERNiCu-7 (AWS A5.14) |
| Typical Forms & Standards | Pipe/tube ASTM B161/B163/B474; sheet/plate ASTM B162; bar ASTM B160; fittings ASTM B366; forgings ASTM B564 | Pipe ASTM B165; welded pipe/tube ASTM B474; sheet ASTM B127; bar ASTM B164; fittings ASTM B366; forgings ASTM B564 |
When to specify Nickel 201:
Caustic soda/potash evaporators, piping, and reactors — particularly at high concentration, high temperature, or molten/fused caustic
Chlor-alkali (ion-membrane and diaphragm cell) process equipment
Food and dairy processing equipment subject to hot caustic CIP cycles
Electroplating anodes, baskets, and bus bars
Deep-drawn or stamped thin-gauge components requiring maximum formability
When to specify Monel 400:
Hydrofluoric acid and fluorine gas handling (alkylation units, HF piping)
Seawater and marine piping, pump/propeller shafts, and fasteners
Non-oxidizing dilute sulfuric or hydrochloric acid service
Applications needing higher as-supplied mechanical strength than commercially pure nickel provides
General chemical processing where good machinability simplifies fabrication
Is Nickel 201 Safe for Food-Contact Equipment?
Generally yes, and it is widely selected for that purpose. Nickel 201's resistance to caustic cleaning solutions and its non-contaminating surface make it a common choice for dairy, food, and beverage processing equipment. That said, alloy chemistry alone doesn't constitute a food-contact certification — confirm the specific finished component meets the applicable FDA, EU, or local food-safety requirements before specifying it for direct food contact.
What Is the Maximum Service Temperature for Nickel 201?
Up to 1,250°F (677°C) for ASME-code pressure vessel construction. This is significantly higher than Nickel 200's practical 600°F (315°C) limit, because Nickel 201's ultra-low carbon content avoids the graphitization that can embrittle Nickel 200 at elevated temperature. Actual allowable design temperature still depends on the applicable ASME code edition, allowable stress table, and the specific service environment.
Can Nickel 201 Be Welded, and What Filler Metal Should Be Used?
Yes — Nickel 201 has excellent weldability. The standard matching filler metal is ERNi-1 per AWS A5.14, used with GTAW or GMAW. Its low carbon content also reduces the risk of carbide-related weld-zone problems compared to higher-carbon Nickel 200.
Should I Choose Nickel 201 or Monel 400 for Hydrofluoric Acid Service?
Monel 400. It is the traditional workhorse alloy for anhydrous and aqueous HF acid, offering outstanding resistance across a wide range of concentrations and temperatures under non-oxidizing conditions. Nickel 201 is primarily selected for caustic/alkaline media rather than HF acid service.
Should I Choose Nickel 201 or Monel 400 for Caustic Soda Service?
Nickel 201, especially at high concentration, high temperature, or molten caustic. Both alloys handle caustic soda well across the concentration range, but Nickel 201's higher nickel content and ASME-approved 1,250°F rating make it the preferred choice for the most demanding caustic duty, such as fused-caustic handling.
Why Does Nickel 201 Replace Nickel 200 in High-Temperature Service?
Because of the carbon content difference. Nickel 201's 0.02% carbon ceiling (versus 0.15% for Nickel 200) prevents the graphite precipitation at grain boundaries that can occur in Nickel 200 during prolonged exposure above roughly 600°F (315°C), which is why Nickel 201 — not Nickel 200 — is the material approved for the higher ASME temperature rating.
Is Nickel 201 Magnetic?
Yes. Nickel 201 is ferromagnetic at room temperature, with a Curie point around 354°C (670°F) — well above typical ambient and moderate service temperatures. This is different from Monel 400, whose Curie point sits close to room temperature, making it only weakly or unreliably magnetic under normal conditions.
Does Nickel 201 Require Post-Weld Heat Treatment?
Not typically for standard service. Nickel 201 is a solid-solution material rather than a precipitation-hardening alloy, so welding does not introduce a hardening reaction that requires PWHT. Stress relief may be specified for demanding service conditions or thick sections, but it is not a standard requirement for routine fabrication.
