ASTM B161

USED FOR:

Seamless pipe and tube manufactured from commercially pure wrought nickel.

ASTM B161 covers seamless pipe and tube manufactured from UNS N02200 (Nickel 200) and UNS N02201 (Nickel 201) wrought nickel., it is a narrower-scope standard than B622, covering essentially pure nickel product rather than the broader nickel-chromium-molybdenum alloy family, and it covers both pipe and tube within the same specification.

RELATED STANDARDS:

• Sibling specs: ASTM B622 covers seamless nickel-alloy pipe for the broader alloy family (Monel 400, Inconel 600/625, Hastelloy C-276, Incoloy 825, etc.) and is the standard to reach for once the material moves beyond commercially pure nickel into an alloyed composition. ASTM B725 covers welded nickel-alloy pipe with a defined joint-efficiency system, used where B161’s seamless-only scope doesn’t fit the intended manufacturing route or diameter. ASTM B165 covers seamless Monel 400 (nickel-copper) pipe and tube specifically, worth noting since Monel is sometimes mentally grouped with “nickel pipe” even though it falls under B165/B622 territory, not B161.
• Design code that invokes it: ASME B31.3 (process piping) references B161 for pure nickel piping in caustic and other specific corrosive services; ASME Section VIII references it for pure nickel vessel piping/nozzles where caustic or specific chemical compatibility with pure nickel (rather than an alloyed nickel) is required.
• Dimensional standard that pairs with it: Dimensions are specified by ASTM B161 and applicable ASME dimensional standards where appropriate, together with project requirements, though as with other nickel-alloy pipe, project-specific or manufacturer-specific OD/WT combinations are common given the specialized, lower-volume nature of pure nickel pipe production.

GRADE / TYPE RANGE:
B161 covers essentially two grades: Nickel 200 and Nickel 201.

Nickel 201 is simply a low-carbon version of Nickel 200, with carbon content capped low enough to avoid graphitization and embrittlement at elevated temperature (roughly above 315°C/600°F) , this is the single defining reason the two grades exist.

Mechanically, the two grades are very similar at room temperature, but Nickel 200 is not recommended for higher-temperature service due to the graphitization risk, making Nickel 201 the default choice whenever elevated temperature is part of the service profile.

Unlike alloy grade selection in B622 (driven by corrosion species), the grade decision in B161 is driven almost entirely by temperature, this is a much simpler selection exercise than most other nickel-alloy specs.

DESCRIPTION:
B161 covers pipe and tube produced by hot working followed by cold finishing where required, with a final anneal to develop the correct grain structure and ductility,  pure nickel’s mechanical behavior and workability are quite different from stainless or alloyed nickel products, and manufacturers need to control annealing carefully to avoid excessive grain growth or inadequate softness for subsequent forming.

Testing requirements include tensile testing, flattening or flaring test, hydrostatic or eddy-current/ultrasonic testing as alternatives, and grain size verification. Because pure nickel is primarily selected for its exceptional resistance to caustic (sodium and potassium hydroxide) environments and specific chemical processes, testing and inspection are less about corrosion-species-specific qualification (as with B622 alloys) and more about basic mechanical and dimensional conformance. Marking requirements identify manufacturer, grade (200 or 201), and heat number, using marking methods that avoid contamination or surface damage that could compromise the material’s corrosion performance.

TYPICAL INDUSTRY USE:
Used almost exclusively in caustic soda (NaOH) production and handling, chlor-alkali plants, and other chemical processes where pure nickel’s specific resistance to caustic environments (superior to nickel-alloy or stainless options) is the deciding factor, a much narrower application niche than B622.

IMPORTANT NOTES:

• We routinely see B161 confused with B622 by engineers assuming “nickel pipe” is a single category, if the service is caustic-specific, B161 (pure nickel) is usually correct; if the service involves chlorides, sour gas, or high-temperature oxidizing/reducing environments, B622’s alloyed grades (625, C-276, 825, etc.) are almost always the better and often the only technically appropriate choice,  pure nickel is not a general-purpose corrosion-resistant material.

• The Nickel 200 vs. 201 decision is one of the most commonly missed details in caustic service specifications, we always double-check the actual operating temperature against the graphitization threshold before accepting Nickel 200 on any line with meaningful thermal cycling or sustained elevated temperature, since specifying the standard grade in a hot caustic line is a known cause of embrittlement failures.

• Additional purchaser requirements may include supplementary inspections or testing as specified by the project or procurement specification, worth confirming case by case rather than assuming a standard supplement package exists.

• NACE MR0175/ISO 15156 is rarely the driving consideration for B161 material given its caustic-specific application niche, but if the same line ever transitions into a sour or chloride-bearing zone, we’d flag that pure nickel is not typically the material of choice there in the first place, that’s usually a sign the piping material selection itself needs review, not just a NACE compliance check.

• Given how narrow and low-volume this product niche is, we consistently find very few qualified suppliers and long lead times, we recommend engaging procurement and the vendor list extremely early on any project specifying B161 pipe, since it is rarely a stock item and is almost always made to order.