ASTM B161 Nickel 201 Pipe

ASTM B161 Nickel 201 Pipe is the low-carbon version of commercially pure nickel. That one change - carbon dropped from 0.15% max in Nickel 200 to 0.02% max in Nickel 201 - is the whole reason the grade exists. Above 315 °C, carbon in Nickel 200 precipitates at grain boundaries as graphite and embrittles the metal. Nickel 201 stops that.

 

If your line handles hot caustic soda, molten salts, or high-temperature reducing acids, Nickel 201 is usually the starting point. This page covers what you need to specify and verify: the chemistry, the mechanical and physical properties, the corrosion boundaries, the sizes and standards, and the checks that prove you received real N02201.

The Carbon Boundary: Why Nickel 201 Exists

Nickel 200 and Nickel 201 are nearly identical in corrosion resistance, electrical conductivity, and forming behavior. The only meaningful difference is carbon.

Grade	UNS	C max	Typical C	Use Above 315 °C?
Nickel 200	N02200	0.15 %	0.06 %	No - graphitization risk
Nickel 201	N02201	0.02 %	0.01 %	Yes - stable microstructure

The 0.02% carbon limit is what lets Nickel 201 operate long-term at temperatures up to about 540 °C in caustic and reducing service. For service below 315 °C, Nickel 200 and Nickel 201 are interchangeable. Above that temperature, Nickel 201 is the only safe choice among commercially pure nickels.

 

Chemical Composition (ASTM B161)

Element	Specification (wt %)	Typical
Nickel (Ni) + Cobalt (Co)	≥ 99.0	99.6
Carbon (C)	≤ 0.02	0.005
Iron (Fe)	≤ 0.40	0.20
Manganese (Mn)	≤ 0.35	0.20
Silicon (Si)	≤ 0.35	0.15
Copper (Cu)	≤ 0.25	0.10
Sulfur (S)	≤ 0.010	0.005

When you check the MTR, focus on carbon first. A certificate showing 0.03% C is not Nickel 201. It does not matter what the supplier calls it - above 0.02% carbon, the pipe is not N02201.

 

Mechanical Properties (ASTM B161 Annealed Pipe)

Property	Minimum	Typical
Tensile strength	380 MPa (55 ksi)	450 MPa
Yield strength, 0.2% offset	80 MPa (12 ksi)	150 MPa
Elongation in 50 mm	35 %	45–55 %
Hardness (typical annealed)	-	45–70 HRB

Nickel 201 work-hardens rapidly. Cold-worked or stress-relieved tube can be supplied at higher strength, but most process piping uses the annealed condition for formability and weldability.

 

Physical Properties That Matter for Design

Property	Value
Density	8.89 g/cm³
Melting range	1435 – 1445 °C
Thermal conductivity @ 20 °C	70 W/m·K
Electrical resistivity	0.095 µΩ·m
Modulus of elasticity	207 GPa
Thermal expansion (20–100 °C)	13.3 µm/m·°C
Curie temperature	~ 360 °C
Magnetic behavior	Ferromagnetic below Curie point; paramagnetic above

The Curie point is worth remembering. Nickel 201 is magnetic at room temperature. In high-temperature instrumentation or electronics applications, the loss of ferromagnetism above ~360 °C can matter for sensor housings and shielding designs.

 

Corrosion Resistance: Where It Works - and Where It Does Not

Environment	Nickel 201 Performance
Caustic soda (NaOH), all concentrations, up to ~540 °C	Excellent - the classic Nickel 201 service
Caustic potash (KOH), neutral and alkaline salts	Excellent
Reducing acids (dilute HCl, H₂SO₄) without oxidizers	Good to excellent
Chloride-free reducing environments	Excellent
Hydrogen fluoride (anhydrous HF)	Good, but Monel 400 is usually preferred
Oxidizing acids (nitric, chromic)	Poor - use stainless or Inconel instead
Wet chlorine / oxidizing chloride solutions	Not suitable
Seawater / neutral chloride service	Good, but 316L or Monel 400 often more cost-effective

 

Sizes, Forms and Standards

Form	Standard	Typical Range
Seamless pipe	ASTM B161 / ASME SB161	NPS 1/8" – 8" (10.3 – 219.1 mm OD), Sch 5S – 160S
Seamless condenser / heat exchanger tube	ASTM B163 / ASME SB163	OD 6.35 – 127 mm, wall 1.27 – 12.7 mm
Welded pipe	ASTM B725 / ASME SB725	Larger diameters on request
Cut lengths	-	Random 3–7 m or fixed to drawing, plain or bevelled

Most inquiries we handle are for ASTM B161 seamless pipe in NPS 1/2" to 4", Sch 40S and 80S, annealed condition. For heat exchangers, ASTM B163 tube is the common call-out.

 

Typical Applications

Industry	Where Nickel 201 Pipe Is Used
Caustic soda / chlor-alkali	Evaporator tubes, concentrator piping, caustic transfer lines
Chemical processing	Hot alkaline reactors, salt production equipment
Food / pharmaceutical	High-purity piping where product cleanliness matters
Electronics / batteries	High-purity nickel components, cathode/anode hardware
Power generation	Heat exchanger tubing, high-temperature gas handling
Synthetic fiber	Spinning jets and process piping in alkaline media

 

Nickel 201 vs Nickel 200 vs 316L: Quick Decision Table

Criterion	Nickel 201 (N02201)	Nickel 200 (N02200)	316L (S31603)
Carbon limit	0.02 % max	0.15 % max	0.03 % max
Max service temp	~ 540 °C	~ 315 °C	~ 425 °C (oxidation limited)
Caustic soda resistance	Excellent	Excellent	Good, limited by chlorides
Oxidizing acid resistance	Poor	Poor	Good
Magnetic at room temp	Yes	Yes	No
Relative price	Higher than 200	Lower than 201	Usually lowest

If your service is hot caustic and the temperature exceeds 315 °C, Nickel 201 is the clear choice. For oxidizing or chloride-bearing service, move to 316L or a higher alloy.

 

 

 

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