Excellent Corrosion Resistance of Hastelloy B2
Hastelloy B2 is a nickel-molybdenum alloy known for its outstanding resistance to strong reducing agents, particularly hydrochloric acid, even in highly concentrated and hot conditions. It also resists corrosion from pure sulfuric, acetic, and phosphoric acids. With low carbon and silicon content, Hastelloy B2 offers enhanced resistance to intergranular attack and stress corrosion cracking.
This article introduces the composition, properties, and applications of Hastelloy B2 to support informed material selection in demanding engineering environments.
What is Hastelloy B2?
Hastelloy B2 (UNS N10665) is a wrought, corrosion-resistant alloy developed for use in highly reducing chemical environments. It is especially effective in applications involving hydrochloric acid at all concentrations and temperatures. The low carbon and iron content improve weldability and resistance to grain boundary precipitation.
Hastelloy B2 Equivalent Grades
| Standard / System | Equivalent Designation |
| UNS | N10665 |
| ASTM / ASME | ASTM B333, B335, B622, B619 |
| EN / DIN | 2.4617 |
| ISO | NiMo28 |
| JIS | NW0665 |
Hastelloy B2 Chemical Composition
| Element | Content (%) |
| Nickel (Ni) | Balance |
| Molybdenum (Mo) | 26.0 – 30.0 |
| Iron (Fe) | ≤ 2.0 |
| Chromium (Cr) | ≤ 1.0 |
| Cobalt (Co) | ≤ 1.0 |
| Carbon (C) | ≤ 0.01 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 0.10 |
| Sulfur (S) | ≤ 0.03 |
Hastelloy B2 Mechanical Properties
| Property | Typical Value |
| Tensile Strength | 690 – 760 MPa |
| Yield Strength | ≥ 240 MPa |
| Elongation | ≥ 40% |
| Hardness (HBW) | ~200 |
Hastelloy B2 Physical Properties
| Property | Value |
| Density | 9.24 g/cm³ |
| Melting Point | 1330 – 1380 °C |
| Thermal Conductivity | ~21 W/m·K |
| Electrical Resistivity | ~1.1 µΩ·m |
| Modulus of Elasticity | ~200 GPa |
| Service Temperature Range | -196 °C to ~400 °C |
Applications of Hastelloy B2
- Hydrochloric Acid Processing: Excellent resistance to HCl across all concentrations.
- Chemical Reactors & Heat Exchangers: For strongly reducing media.
- Pickling Equipment: Handles highly corrosive pickling solutions.
- Pharmaceutical and Fine Chemicals: For equipment requiring minimal metal ion leaching.
- Pesticide and Dye Manufacturing: Durable under harsh organic acids.
Advantages of Hastelloy B2
- Outstanding resistance to hydrochloric acid, even under boiling conditions.
- Superior performance in reducing environments, such as acetic and phosphoric acids.
- Low carbon and silicon content: Minimizes risk of grain boundary precipitation.
- Good weldability: Suitable for fabrication without post-weld heat treatment.
- Resistant to stress corrosion cracking and pitting under appropriate conditions.
Limitations of Hastelloy B2
- Not suitable for oxidizing environments (e.g., nitric acid, ferric or cupric salts).
- Challenging to machine: Requires specialized tools and techniques.
- Expensive: High nickel and molybdenum content drive cost.
- May suffer from localized corrosion if exposed to oxidizers, even briefly.
Hastelloy B2 vs Other Alloys
| Feature | 316L | 904L | Hastelloy B2 |
| Acid Resistance | Moderate | High | Exceptional (reducing acids) |
| Chloride Resistance | Moderate | High | Moderate |
| Molybdenum Content | ~2.0% | ~4.5% | ~28% |
| Oxidizer Resistance | Fair | Good | Poor |
| Cost | Low | High | Very High |
FAQ About Hastelloy B2
B2 is superior in reducing environments (e.g., HCl)
C276 performs better in oxidizing and mixed-acid environments
Yes, it is weldable using common methods such as GTAW (TIG) and GMAW (MIG).
Post-weld annealing is recommended to restore corrosion resistance.
Summary
This article presents Hastelloy B2 as a reliable solution for highly corrosive reducing environments. With its exceptional resistance to hydrochloric acid and other aggressive chemicals, it is widely used in critical chemical processing and pharmaceutical systems.
MT.BOLTS offers high-quality Hastelloy B2 fasteners, flanges, and fittings tailored for use in severe environments. Contact us today or visit our website to learn more or request a quote.
