Hastelloy Family Guide: C276 vs C22 vs B3 vs X — Selection & Application

Understanding the Hastelloy Family

Hastelloy is the trade name for a family of nickel-molybdenum and nickel-chromium-molybdenum alloys developed primarily for corrosive chemical processing environments. Unlike Inconel (which prioritizes high-temperature strength), Hastelloy alloys are optimized for resistance to acids, chlorides, and mixed corrosive media at moderate temperatures.

The family divides roughly into:

• C-family (C276, C22, C2000): chromium-molybdenum alloys — best for oxidizing+reducing mixed media
• B-family (B3, B2): nickel-molybdenum alloys — best for hydrochloric acid and reducing acids
• X-family (X): nickel-chromium-iron-molybdenum — designed for high-temperature oxidation, not room-temperature corrosion

Chemical Composition Comparison

Grade	Ni	Cr	Mo	W	Cu	Fe
C276	57	16	16	4	—	5
C22	56	22	13	3	—	3
C2000	59	23	16	—	1.6	3
B3	65	1.5	28.5	—	—	1.5
X	47	22	9	—	—	18

Balance = C276 57+16+16+4+5 = 98 (remainder Co+other). B3: Ni+Mo+Cr+Fe ≈ 97. Values are typical wt%, confirm with mill certificate.

Corrosion Resistance: When to Use Each Grade

C276 — The Universal Choice

C276 is the most widely used Hastelloy grade. It handles hydrochloric acid at all concentrations up to boiling, hypochlorite solutions, acetic acid, and chloride-rich media. It is the standard choice for:

• Chemical process vessels and reactors
• Flue gas desulfurization (FGD) scrubbers
• Pharmaceutical API synthesis vessels
• Pulp and paper bleach plants
• Offshore oil and gas produced water

Limitation: in strongly oxidizing media (hot concentrated nitric acid, ferric chloride solutions above 1%), C276 can suffer edge erosion. For those conditions, use C22.

C22 — The Oxidizing Media Specialist

C22's higher chromium (22% vs 16%) gives it superior resistance to oxidizing acids and oxidizing salts: nitric acid, ferric chloride, cupric chloride, and mixed oxidizing media. It is the preferred choice for:

• Mixed acid service (H2SO4 + HNO3)
• Pharmaceutical oxidative processes
• Pollution control equipment with biocides
• 浪涌曝气系统 (surge aeration systems)

C22 also has better weldability than C276 — it does not require post-weld heat treatment and is less crack-sensitive. For vessels where field welding is required, C22 is often the safer choice.

B3 — Hydrochloric Acid Specialist

B3 (N10675) is the upgrade from B2. The key difference: B3 eliminates the knife-line attack and HAZ degradation problems that plagued B2 welds. B3 has excellent resistance to:

• Hydrochloric acid (HCl) — all concentrations at temperatures up to boiling
• Sulfuric acid (H2SO4) — up to 60% concentration
• Phosphoric acid (H3PO4) — at moderate temperatures

Do NOT use B3 in oxidizing media — even small amounts of ferric ions or cupric ions can cause rapid attack. B3 is for purely reducing acid environments.

X — High Temperature Only

X is designed for 1200°C maximum service temperature. It maintains strength and forms a protective chromia oxide scale at these temperatures. Best for:

• Aircraft and industrial gas turbine combustion zones
• Industrial furnace muffles and radiant tubes
• Afterburner and exhaust hardware
• Petrochemical reformer internals above 900°C

For temperatures below 650°C where strength is needed: Inconel 625 or 718 are usually better choices with superior corrosion resistance in most process environments.

Grade Selection Decision Tree

Weldability and Fabrication

Grade	Difficulty	Filler Wire	Interpass Temp	PWHT Required?
C276	Moderate-High	ERNiCrMo-4	<100°C	No
C22	Moderate	ERNiCrMo-4	<120°C	No
B3	Moderate	ERNiMo-10	<120°C	No (but verify)
X	Moderate	ERNiCrMo-2 or 625	<150°C	No

Cost & Availability

C276 is the most commonly stocked grade — most mills produce it to ASTM B574 (rod), B575 (plate/sheet), B622 (seamless tube), B619 (welded pipe). Lead times are typically 4-8 weeks for mill orders, 1-2 weeks for distributors with stock.

C22 costs approximately 10-15% more than C276 due to higher chromium content and less common usage. B3 is comparable to C276 or slightly higher. X is generally most expensive due to aerospace demand and tighter tolerance requirements.

For castings: ASTM A494 defines CW-12MW (equivalent to C276), CW-6M (C22), CW-12MW-1 (B3). Note that cast grades have slightly different composition ranges than wrought — verify with your foundry.

How to Specify Hastelloy for Your RFQ

When sending an RFQ for Hastelloy components, include:

• UNS number (e.g., N06022 for C22) — this eliminates grade ambiguity
• ASTM/ASME specification (B575 for plate, B622 for tube, etc.)
• Form and dimensions (plate thickness, tube OD/wall, bar diameter)
• Form (solution annealed + pickled is standard; ground and polished for tube ID)
• Testing requirements (PMI verification, hydrostatic test, EN 10204 3.1 mill cert)
• Quantity and target delivery date