Hastelloy B-3
A nickel-molybdenum alloy for reducing acids
Typical values for the temper in the title
Hastelloy B-3 contains at least 65% nickel and 27–32% molybdenum, with a little chromium. It is built for "reducing" environments, especially hydrochloric acid at almost any concentration and temperature, where most other metals fail quickly.
B-3 is an improved generation of B-2, with a more stable structure during welding and hot working. It is used in tanks, piping and heat exchangers in the chemical industry, in reducing hydrochloric, sulfuric and phosphoric environments.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 790 MPa | |
| Yield strength Rp0.2 | 380 MPa | |
| Elongation A | 60% | |
| Modulus of elasticity E | 216 GPa | |
| Density ρ | 9.22 g/cm³ | |
| Hardness | about 95 HRB (database value) | annealed |
| Machinability | 30% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Ni nickel | min 65.0 | |
| Mo molybdenum | 27.0–32.0 | reducing-acid resistance |
| Cr chromium | 1.0–3.0 | structural stability |
| Fe iron | 1.0–3.0 | |
| W tungsten | max 3.0 | |
| Co cobalt | max 3.0 | |
| Mn manganese | max 3.0 | |
| C carbon | max 0.01 | |
| Si silicon | max 0.10 |
Ranges per ASTM B619 (UNS N10675).
Conditions and heat treatment
A solid-solution alloy: it is not hardened by heat treatment, and is supplied annealed or cold worked.
| Condition | Properties | When to choose it |
|---|---|---|
| Solution annealed | very ductile | delivery condition |
Applications
- Hydrochloric acid equipment
- Chemical piping and tanks
- Heat exchangers in reducing environments
- Reducing sulfuric acid equipment
- Chemical reactors
Fabrication
Welding
Welds well by TIG and MIG. Careful cleaning before welding is especially important: oil, paint or sulfur on the surface cause weld cracking. With matching filler.
Machining
Nickel alloys work harden, stay strong when hot, and wear tools. Use low speed, a steady feed that does not "rub", sharp rigid tools and plenty of coolant.
Corrosion
A critical limit: ferric (Fe3+) or cupric (Cu2+) ions, or oxygen, in a reducing solution make it oxidizing, and the corrosion rate of B-3 rises sharply.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Hastelloy C-276 | 690–1000 / 350–460 MPa | Good — ERNiCrMo-4 | also resistant in oxidizing environments · material page |
| Inconel 625 | 827–1034 / 414–758 MPa | Excellent — ERNiCrMo-3 | for oxidizing environments and seawater · material page |
| Monel 400 | 480–550 / 170–345 MPa | Good | for hydrofluoric acid and seawater · material page |
Common mistakes
Using B-3 in a solution with ferric or cupric ions
They make the environment oxidizing, and the corrosion rate rises sharply. Check the solution, including contaminants.
Connecting iron or copper equipment in the same system
Their corrosion releases ions into the solution.
Choosing B-3 as a general "safe" alloy
It is excellent only in reducing conditions.
Equivalents, standards and supply
| EN | 2.4600 (NiMo29Cr) |
|---|---|
| Standards | ASTM B333 |
| Forms | plate · rod · pipe |
| Producers | Haynes International |
Learn more
Values are typical and for comparison only. For design, rely on the standard and the mill certificate. Sources: ASTM (B127, B164, B168, B443, B575, B619 and others), Special Metals and Haynes data sheets, and the METAL HUB materials database. Inconel and Monel are trademarks of Special Metals, and Hastelloy of Haynes International.
Updated: October 31, 2026