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Hastelloy B2 (UNS N10665/W.Nr. 2.4617) is a solid solution strengthened nickel molybdenum alloy that exhibits significant resistance to reducing environments such as hydrogen chloride gas, sulfuric acid, acetic acid and phosphoric acid. Molybdenum is a major alloying element that provides significant corrosion resistance in reducing environments. This nickel alloy can be used in the as-welded condition because it resists the formation of grain boundary carbide deposits in the weld heat-affected zone.
In addition, Hastelloy B2 has excellent resistance to pitting corrosion, stress corrosion cracking, and knife line and heat-affected zone attacks. Alloy B2 supports resistance to pure sulfuric acid and many non-oxidizing acids.
Hastelloy B2 is suitable for most chemical process applications in the as-welded state. Ideal for equipment that handles hydrochloric acid of various concentrations and temperatures. Resistant to hydrogen chloride gas and sulfuric acid, acetic acid and phosphoric acid.
The main high temperature applications are those requiring a low coefficient of thermal expansion. Exposure to temperatures between 540 and 815°C (1000-1500°F) should be avoided as the ductility of the alloy decreases. In oxidizing gases such as air, Hastelloy B2 can be used at temperatures up to 540°C (1000°F). In reducing gas or vacuum, the alloy can be used at 815°C (1500°F) to higher temperatures. When hydrochloric acid comes into contact with iron or copper, iron or copper salts may be formed, therefore Hastelloy B2 should not be used with copper or iron piping in systems containing hydrochloric acid.
Grade | Mo | Fe≤ | C≤ | Co≤ | Cr≤ | Mn≤ | Si≤ | P≤ | S≤ | Ni |
Hastelloy B2 | 26.0-30.0 | 2.00 | 0.02 | 1.00 | 1.00 | 1.00 | 0.10 | 0.04 | 0.03 | Remainder |
Tensile, min, ksi[MPa] | Yield, min, ksi[MPa] | Elongation, %(min) |
110[760] | 51[350] | 40 |
| Products | Standards | Show |
| Hastelloy B2 Bars | ASTM B335 |  |
| Hastelloy B2 Sheets/Plates | ASTM B333, A480 |  |
| Hastelloy B2 Welded Pipe | ASTM B619, B775 |  |
| Hastelloy B2 Seamless Pipe | ASTM B622 |  |
| Hastelloy B2 Welded Tube | ASTM B626 |  |
| Hastelloy B2 Fittings | ASTM B366 |  |
| Hastelloy B2 Forgings | ASTM B564 |  |
Grade | Density Room Temp. | Melting Range | Specific Heat 68°F | Elastic Modulus 68°F | Thermal Conductivity 68°F |
Hastelloy B2 | 0.333lb/in3 | 2430°F to 2520°F | 0.090Btu/lb. °F | 31.4*106psi | 64Btu/ft.h.°F |
STANDARD | WERKSTOFF NR. | UNS | EN |
Hastelloy B2 | 2.4617 | N10665 | NiMo28 |
The Hastelloy B series has evolved through three generations. The original B (1920s) had weldability issues.
B2 (1960s) improved weldability with lower C/Si/Fe but suffers from beta-phase embrittlement at 540–815°C.
B-3 (1990s) is the current-generation upgrade that solves B2's embrittlement problem through controlled Cr and Fe additions, enabling as-welded service without mandatory post-weld annealing.
For new projects, B3 is generally recommended over B2.
| Element | Hastelloy B (N10001) | Hastelloy B-2 (N10665) | Hastelloy B-3 (N10675) | Evolution Rationale |
|---|---|---|---|---|
| Nickel (Ni) | Balance (~60%) | Balance (~64%) | Balance (~65%) | Gradually increased for better corrosion resistance |
| Molybdenum (Mo) | 26–30% | 26–30% | 27–32% | Core element for HCl resistance; maintained across generations |
| Iron (Fe) | 4–6% | ≤2% | 1–3% | B-2 reduced Fe for corrosion; B-3 readjusted for phase stability |
| Chromium (Cr) | ≤1% | ≤1% | 1–3% | B-3's key addition: suppresses Ni₄Mo beta-phase precipitation |
| Carbon (C) | ≤0.05% | ≤0.02% | ≤0.01% | Progressively reduced to prevent carbide sensitization |
| Silicon (Si) | ≤1.0% | ≤0.10% | ≤0.10% | B-2/B-3 drastically reduced Si for weldability |
| Cobalt (Co) | ≤2.5% | ≤1.0% | ≤3.0% | Residual; controlled |
| Manganese (Mn) | ≤1.0% | ≤1.0% | ≤3.0% | B-3 allows more for hot workability |
| Aluminum (Al) | — | — | ≤0.50% | B-3 addition: oxidation resistance + deoxidation |
| Titanium (Ti) | — | — | ≤0.20% | B-3 addition: ties up carbon to prevent sensitization |
| Parameter | Hastelloy B | Hastelloy B-2 | Hastelloy B-3 |
|---|---|---|---|
| HCl resistance (all conc./temp.) | Excellent | Excellent | Excellent |
| Thermal stability (550–800°C) | Poor | Poor (beta-phase embrittlement) | Excellent (suppressed beta-phase) |
| As-welded service | Not recommended | Limited (PWHT often required) | Yes (no PWHT needed) |
| Fabrication ease | Difficult | Moderate | Easier |
| Intergranular corrosion resistance | Moderate | Good | Excellent |
| Tensile Strength (min, MPa) | 690 | 760 | 760 |
| Yield Strength (min, MPa) | 310 | 350 | 350 |
| Current market status | Legacy (rarely specified) | Still used (legacy projects) | Current standard (recommended) |
Selection guidance: For new projects, Hastelloy B-3 is recommended over B-2 due to its superior thermal stability, easier fabrication, and ability to enter service in the as-welded condition. B-2 remains available for legacy equipment, repair/replacement of existing B-2 components, and applications where B-2 is specifically required by established specifications. The original Hastelloy B is rarely specified for new construction.
Hastelloy B2 is one of the best commercial alloys for hydrochloric acid service. It resists HCl at all concentrations from dilute to concentrated, and from room temperature to boiling, with corrosion rates typically below 0.5 mm/year. The 26–30% molybdenum content forms a dense Mo-rich passive film that is stable in reducing acid environments.
However, B2 must NEVER be used in HCl containing oxidizing ions (Fe³⁺, Cu²⁺) — even trace amounts (0.005% Fe³⁺) can cause catastrophic failure.
Hydrochloric acid is one of the most aggressive industrial chemicals. It attacks virtually all standard stainless steels, most nickel-chromium alloys, and even titanium. The nickel-molybdenum system is uniquely suited to HCl service because molybdenum forms a stable passive film in reducing (oxygen-free) acid environments that chromium-based passive films cannot maintain.
B2 Performance in Hydrochloric Acid by Concentration & Temperature
| HCl Concentration | Temperature | Corrosion Rate (B2) | Performance Rating |
|---|---|---|---|
| 1–10% (dilute) | Room temp to 70°C | <0.05 mm/year | Excellent |
| 10–20% | Room temp to 70°C | <0.1 mm/year | Excellent |
| 20–37% (concentrated) | Room temp | <0.1 mm/year | Excellent |
| 1–10% (dilute, boiling) | ~105°C (boiling) | <0.3 mm/year | Very good |
| 10–20% (boiling) | ~110°C (boiling) | 0.3–0.5 mm/year | Good |
| 37% (concentrated, boiling) | ~110°C | 0.5–1.0 mm/year | Moderate (verify by test) |
| Any concentration with Fe³⁺ or Cu²⁺ contamination | Any | Rapid failure (>10 mm/year) | DO NOT USE |
Typical Hydrochloric Acid Applications
HCl distillation columns: B2 is the standard material for HCl distillation tower internals, trays, and packing supports where concentrated acid is processed at elevated temperatures.
HCl synthesis reactors: Direct synthesis of HCl from hydrogen and chlorine gas produces ultra-pure acid at high temperature. B2 reactors and heat exchangers handle this severe duty.
Acid recovery and regeneration: Spent HCl from steel pickling or chemical processes is recovered by distillation or evaporation. B2 evaporators and condensers resist the hot concentrated acid.
Pharmaceutical reactors: Many pharmaceutical syntheses use HCl as a reagent or catalyst. B2 reactor vessels and agitators provide long service life in pure HCl environments.
Petrochemical alkylation units: Hydrocarbon alkylation processes use concentrated HCl or H₂SO₄ catalysts. B2 piping and vessels handle the acid catalyst streams.
Steel pickling lines: B2 pickling tank heaters, coils, and baskets resist HCl pickling solutions (5–20% HCl at 60–80°C).
| HCl Condition | Recommended Material | Rationale |
|---|---|---|
| Pure HCl, any concentration, any temperature | Hastelloy B2 or B-3 | Best available resistance; Mo passive film stable |
| HCl with Fe³⁺/Cu²⁺ contamination | Hastelloy C-276 or C-22 | Cr content provides oxidizing-environment resistance |
| HCl with dissolved oxygen | Hastelloy C-276 | More tolerant of oxidizing conditions than B2 |
| Dilute HCl at ambient temperature | Hastelloy C-276 or zirconium | C-276 adequate for dilute; zirconium for pure acid |
| Concentrated HCl at boiling | Hastelloy B-3 (preferred) or B2 | B-3 better thermal stability; both excellent in pure HCl |
| HCl + H₂SO₄ mixed acid | Hastelloy B2/B-3 (if pure) or C-276 (if oxidizing) | Depends on oxidation state of the mixture |
Corrosion Resistance:
Regarding general corrosion, Hastelloy B2 alloy's resistance to inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid is essentially the same as that of Hastelloy B alloy. However, its corrosion resistance is generally superior to that of Hastelloy B alloy, particularly after welding. In 20% boiling hydrochloric acid, even cold working deformation of Hastelloy B2 up to 50% does not affect its corrosion resistance.
Regarding intergranular corrosion, due to the lower carbon, silicon, and iron contents of Hastelloy B2 alloy, the carbides and intermetallic phases in the sensitized steel are far less than those in Hastelloy B alloy. Therefore, this alloy exhibits superior resistance to intergranular corrosion.
Regarding stress corrosion, tests have shown that when Hastelloy B2 alloy contains low residual Fe ≤ 2% and Cr ≤ 1.0%, the stress corrosion resistance of the latter alloy is superior to that of the same alloy with appropriately controlled Fe and Cr contents after medium-temperature aging.
Mechanical Properties:
The ductility of Hastelloy B2 alloy decreases and worsens with aging. This is due to the precipitation of the hard and brittle β phase during the intermediate-temperature aging process.
Weldability:
Hastelloy B2 alloy offers excellent weldability. Due to its low carbon, silicon, and iron content, it exhibits superior resistance to post-weld intergranular corrosion and knife-edge corrosion compared to Hastelloy B. When the iron and chromium content is properly controlled, Hastelloy B2's ductility, toughness, corrosion resistance, and weldability are further enhanced. Therefore, Hastelloy B2 generally does not require post-weld heat treatment. This alloy is more suitable for manufacturing welding equipment and components than Hastelloy B.
Heat Treatment:
Except for applications specified otherwise, this alloy requires solution treatment at 1066°C before use. Unless the Fe+Cr content in the alloy is carefully controlled, prolonged use at temperatures between 538°C and 816°C is generally not permitted.
Food Processing Industry
Fabrication Industry
Oil and Gas Industry
Chemical Industry
Plumbing
General Purpose Applications
Water supply Systems
Power Plant
Paper & Pulp Industry
Q: What is Hastelloy B2 used for?
Hastelloy B2 is used for equipment handling hydrochloric acid at all concentrations and temperatures, including distillation columns, reactors, heat exchangers, and piping. It is also used in sulfuric acid, acetic acid, and phosphoric acid service in reducing conditions. Typical industries include chemical processing, pharmaceuticals, petrochemicals, and steel pickling.
Q: What is the difference between Hastelloy B2 and B3?
B3 is the next-generation upgrade of B2. B3 has superior thermal stability, resisting the formation of brittle Ni₄Mo (beta phase) that plagues B2 in the 550–800°C range. B3 can be used in the as-welded condition without mandatory post-weld solution annealing, while B2 often requires it. Both have similar hydrochloric acid corrosion resistance. B3 is easier to fabricate and is generally recommended for new projects.
Q: Can Hastelloy B2 be used in hydrochloric acid?
Yes. Hastelloy B2 is one of the best materials available for hydrochloric acid service. It resists HCl at all concentrations from dilute to concentrated, and from room temperature to boiling. Corrosion rates are typically below 0.5 mm/year across the full concentration-temperature range. However, B2 must NOT be used in HCl containing oxidizing ions (Fe³⁺, Cu²⁺) — even 0.005% Fe³⁺ can cause rapid failure.
Q: What are the limitations of Hastelloy B2?
B2 has three key limitations: (1) It is susceptible to beta-phase (Ni₄Mo) embrittlement when exposed to temperatures between 540–815°C, requiring mandatory post-weld solution annealing. (2) It has very low chromium content (<1%), making it unsuitable for oxidizing environments, oxidizing acids, or media containing Fe³⁺/Cu²⁺ ions. (3) It should not be used with copper or iron piping in HCl systems to avoid galvanic contamination.
Q: Is Hastelloy B2 magnetic?
No. Hastelloy B2 is a fully austenitic nickel-molybdenum alloy with a face-centered cubic (FCC) crystal structure. It is non-magnetic in the solution-annealed condition.
Q: What welding consumables are used for Hastelloy B2?
The recommended filler metal for Hastelloy B2 is ERNiMo-7 (AWS A5.14) for GTAW/GMAW, or ENiMo-7 for SMAW. Use low heat input, interpass temperature below 100°C, and ensure thorough cleaning of the weld zone. Post-weld solution annealing at 1,066°C is recommended for critical service to restore full corrosion resistance in the heat-affected zone.
Q: What is the maximum service temperature of Hastelloy B2?
In oxidizing environments such as air, the maximum service temperature is 540°C (1,000°F). In reducing gas or vacuum, it can be used up to 815°C (1,500°F) or higher. However, prolonged exposure between 540–815°C must be avoided due to beta-phase (Ni₄Mo) precipitation that causes embrittlement and loss of corrosion resistance.
Q: Why was Hastelloy B2 developed to replace Hastelloy B?
Hastelloy B2 was developed to solve two problems with the original Hastelloy B: (1) reduced carbon and silicon content to minimize carbide precipitation and improve weldability, and (2) reduced iron content from <6% to <2% to improve corrosion resistance after welding. B2 offers superior resistance to intergranular and knife-edge corrosion compared to the original B alloy.
Q: Can Hastelloy B2 be used in sulfuric acid?
Yes, but only in pure (non-oxidizing) sulfuric acid. B2 provides excellent resistance to pure sulfuric acid at moderate concentrations and temperatures. However, it is not suitable for sulfuric acid containing oxidizing contaminants (Fe³⁺, Cu²⁺, dissolved oxygen). For mixed or oxidizing acid service, Hastelloy C-276 or C-22 is recommended instead.
Q: Should I choose B2 or B3 for a new project?
For new projects, B3 is generally recommended. It offers the same hydrochloric acid corrosion resistance as B2 but with dramatically improved thermal stability, easier fabrication, and the ability to enter service in the as-welded condition without mandatory post-weld solution annealing. B2 remains appropriate for repair/replacement of existing B2 equipment or where specifications mandate B2.
Q: What is the minimum order quantity for Hastelloy B2?
For standard stock items, we can supply from 1 piece. For custom-cut or made-to-order items, the MOQ is typically 100kg. Contact our sales team with your specific requirements for a detailed quotation.
