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Hastelloy B3 is a nickel-molybdenum alloy of the Hastelloy B series. It optimizes the composition based on the B2 alloy to improve thermal stability, intergranular corrosion resistance and welding performance. The core advantage is its excellent corrosion resistance to strong reducing media, while solving the problem of the early B series alloys easily precipitating brittle phases after hot working or welding. At the same time, Hastelloy B3 alloy has excellent corrosion resistance to hydrochloric acid at any temperature and concentration.
Hastelloy B3 can also withstand non-oxidizing media such as sulfuric acid, acetic acid, formic acid, and phosphoric acid.The distinguishing feature of Hastelloy B3 is that it retains excellent ductility during transient exposure to moderate temperatures. This exposure often occurs during thermal processing associated with manufacturing.
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| Composition | Value |
| C≤ | 0.01 |
| Mn≤ | 3.0 |
| P≤ | 0.03 |
| S≤ | 0.01 |
| Si≤ | 0.01 |
| Ni≤ | 65.0 |
| Cr | 1.0-3.0 |
| Mo | 27.0-32.0 |
| Fe | 1.0-3.0 |
| Co≤ | 3.0 |
| V≤ | 0.2 |
| Properties | Value |
| Tensile Strength | 760MPa |
| Yield Strength | 350MPa |
| Elongation | 40% |
| Product | Standard | Show |
| Hastelloy B3 Sheet Plate | ASTM B333 |  |
| Hastelloy B3 Bars | ASTM B335 |  |
| Hastelloy B3 Seamless Pipe And Tube | ASTM B622 |  |
| Hastelloy B3 Welded Pipe And Tube | ASTM B619/B626 |  |
| Hastelloy B3 Fittings | ASTM B366 |  |
| Hastelloy B3 Forgings | ASTM B564 |  |
| Hastelloy B3 Coated Electrodes | DIN 2.4696 |  |
| Hastelloy B3 Bare Welding Rods And Wire | DIN 2.4695 |  |
Density | Thermal Conductivity | Specific Heat | Melting Range | ||||
lb/in3 | g/cm3 | Btu.in/h.ft2.°F | W/m.°C | Btu/lb.°F | J/kg*°C | °F | °C |
0.333 | 9.22 | 78 | 11.2 | 0.089 | 373 | 2500-2585 | 1370-1418 |
| Standard System | Designation |
|---|---|
| UNS (USA) | N10675 |
| DIN / W.Nr. (Germany) | 2.4600 |
| EN (Europe) | NiMo29Cr |
| JIS (Japan) | NW 6750 |
| GB (China) | NS 3203 (Hastelloy B-3 equivalent) |
Hastelloy B3 is one of the best commercial alloys for hydrochloric acid service, matching B-2's performance across the full concentration and temperature range. 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 27–32% molybdenum content forms a dense Mo-rich passive film in reducing acid. However, B-3 must NEVER be used in HCl containing oxidizing ions — even trace amounts 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.
B-3 Performance in Hydrochloric Acid by Concentration & Temperature
| HCl Concentration | Temperature | Corrosion Rate (B-3) | 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 |
Critical Warning — Oxidizing Ion Contamination: Hastelloy B-3 must NEVER be used in hydrochloric acid containing oxidizing ions such as Fe³⁺ (ferric) or Cu²⁺ (cupric). Even trace amounts — as little as 0.005% (50 ppm) Fe³⁺ — will oxidize and dissolve the Mo-rich passive film, causing corrosion rates to jump from <0.1 mm/year to >10 mm/year. This is the single most common cause of B-series alloy failure in chemical plants.
Iron piping or equipment upstream: Dissolved iron from carbon steel or cast iron components enters the HCl stream as Fe²⁺, which oxidizes to Fe³⁺ in the presence of air.
Copper heat exchanger tubes: Copper dissolves in HCl and forms Cu²⁺ ions. Never use B-3 with copper piping in HCl systems.
Aeration: Dissolved oxygen in HCl can act as a weak oxidizer, especially at elevated temperatures. Degas or inert the acid for best performance.
Oxidizing additives: Some process streams add oxidizing agents (H₂O₂, HNO₃, chlorine) that destroy the B-3 passive film.
HCl distillation columns: B-3 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. B-3 reactors handle this severe duty without PWHT.
Acid recovery and regeneration: Spent HCl from steel pickling or chemical processes is recovered by distillation or evaporation. B-3 evaporators and condensers resist the hot concentrated acid.
Pharmaceutical reactors: Many pharmaceutical syntheses use HCl as a reagent or catalyst. B-3 reactor vessels and agitators provide long service life and can be used as-welded.
Herbicide and insecticide production: Agricultural chemical synthesis often involves HCl. B-3 reactors and piping handle the reducing acid environment.
Acetic acid and ethylene glycol production: B-3 resists acetic acid and the HCl catalysts used in ethylene glycol production.
Hydrochloric Acid
B-3's primary application is resistance to hydrochloric acid at all concentrations and temperatures. In pure, deaerated HCl, B-3's corrosion rate is typically below 0.1 mm/year from room temperature to 70°C across the full concentration range. Even in boiling HCl, B-3 maintains corrosion rates below 0.5 mm/year for most concentrations. Performance is equivalent to B-2.
Sulfuric Acid
B-3 provides excellent resistance to pure (non-oxidizing) sulfuric acid at moderate concentrations and temperatures. In boiling 10% H₂SO₄, corrosion rates are below 0.1 mm/year. Performance degrades at higher concentrations and in the presence of oxidizing contaminants.
Phosphoric Acid
B-3 resists pure phosphoric acid well. For wet-process phosphoric acid containing fluoride and chloride contaminants, B-3 may be specified for the most aggressive high-fluoride stages where its Mo content provides an advantage.
Acetic and Organic Acids
B-3 provides excellent resistance to acetic acid, formic acid, and other organic acids in reducing conditions. It is used in acetic acid production equipment and reactors handling organic acid media.
Stress Corrosion Cracking
B-3 is immune to chloride-induced stress corrosion cracking due to its high nickel content. The improved thermal stability of B-3 also eliminates the beta-phase embrittlement that could mimic SCC behavior in B-2 after intermediate-temperature exposure.
Chemical & Pharmaceutical Industries
Vacumm Furnaces
Manufacturing component for reducing environment
Herbicides, Insecticides, Ethylene glycol and Ethyl benzene production units
Machine Components
Acetic acid production
Q: What is Hastelloy B-3 used for?
Hastelloy B-3 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, formic acid, and phosphoric acid service in reducing conditions. Typical industries include chemical processing, pharmaceuticals, petrochemicals, herbicide/insecticide production, and steel pickling.
Q: What is the difference between Hastelloy B-2 and B-3?
B-3 is the next-generation upgrade of B-2. B-3 has superior thermal stability, resisting the formation of brittle Ni₄Mo (beta phase) that plagues B-2 in the 550–800°C range. B-3 can be used in the as-welded condition without mandatory post-weld solution annealing, while B-2 often requires it. B-3 achieves this by adding 1–3% chromium and 1–3% iron to the Ni-Mo base, which slows beta-phase precipitation kinetics. Both have similar hydrochloric acid corrosion resistance.
Q: Can Hastelloy B-3 be used in hydrochloric acid?
Yes. Hastelloy B-3 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 27–32% molybdenum content forms a dense Mo-rich passive film in reducing acid. However, B-3 must NOT be used in HCl containing oxidizing ions (Fe³⁺, Cu²⁺) — even trace amounts can cause rapid failure.
Q: Does Hastelloy B-3 require post-weld heat treatment?
No, generally not. This is the key advantage of B-3 over B-2. B-3's controlled chromium and iron additions suppress beta-phase (Ni₄Mo) precipitation during the weld thermal cycle, allowing fabrications to enter service in the as-welded condition. B-2, by contrast, often requires mandatory post-weld solution annealing at 1,066°C. Solution annealing at 1,050–1,100°C may still be specified for critical service or optimal properties.
Q: Is Hastelloy B-3 magnetic?
No. Hastelloy B-3 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 B-3?
The recommended filler metal for Hastelloy B-3 is ERNiMo-10 (AWS A5.14) for GTAW/GMAW, or matching B-3 composition filler (DIN 2.4695 wire / DIN 2.4696 electrodes). Use low heat input, interpass temperature below 100°C, and thorough cleaning. Unlike B-2, B-3 does not require mandatory post-weld solution annealing thanks to its superior thermal stability.
Q: What is the maximum service temperature of Hastelloy B-3?
In oxidizing environments such as air, B-3 can be used up to approximately 540°C. In reducing gas or vacuum, it can be used up to 815°C or higher. While B-3 has much better thermal stability than B-2 in the 550–800°C range, prolonged exposure at intermediate temperatures should still be minimized. B-3's key advantage is that transient thermal exposure during welding does not cause the catastrophic embrittlement seen in B-2.
Q: What are the limitations of Hastelloy B-3?
B-3 has two key limitations: (1) It has low chromium content (1–3%), making it unsuitable for oxidizing environments, oxidizing acids (nitric acid), or media containing Fe³⁺/Cu²⁺ ions. (2) It should not be used with copper or iron piping in HCl systems to avoid galvanic contamination. For oxidizing acid service, Hastelloy C-276 or C-22 should be used instead.
Q: Should I choose B-2 or B-3 for a new project?
For new projects, B-3 is strongly recommended over B-2. B-3 offers the same hydrochloric acid corrosion resistance as B-2 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. B-2 remains appropriate for repair/replacement of existing B-2 equipment or where specifications mandate B-2.
Q: Can Hastelloy B-3 be used in sulfuric acid?
Yes, but only in pure (non-oxidizing) sulfuric acid. B-3 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.
