Technical guide · 2026-08-14
Nickel-Chromium-Molybdenum Alloys
Nickel-chromium-molybdenum alloys are corrosion-focused materials for aggressive mixed, reducing and chloride-bearing process streams, where alloy selection must follow full solution chemistry, redox state, temperature and fabrication history.
01
Definition and boundary
Ni-Cr-Mo is not one interchangeable grade family: C-276, 22, 625 and related alloys have different chemistry, code coverage and resistance envelopes.
Reference information only: final acceptance is controlled by the ordered product specification, condition, dimensions and certified test results.
02
How the material system works
Molybdenum improves resistance to reducing acids and localized attack.
Chromium supports oxidizing resistance and passive-film stability.
Tungsten, iron and minor-element control distinguish alloy response and weldability.
03
Representative grades and systems
| Grade or system | Selection focus | Qualification |
|---|---|---|
| Alloy C-276 / UNS N10276 | Versatile high-molybdenum corrosion alloy for severe process service. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| Alloy 22 / UNS N06022 | Higher-chromium Ni-Cr-Mo-W system for mixed oxidizing-reducing environments. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| Alloy 625 / UNS N06625 | Ni-Cr-Mo-Nb alloy combining corrosion resistance and useful strength. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
04
Properties and trade-offs
Resistance to pitting and crevice corrosion
Reducing- and mixed-acid capability
Welded-condition corrosion performance
05
Product forms and supply conditions
06
Applications and selection
Applications and selection
- Flue-gas desulfurization
- Chemical reactors and piping
- Offshore and sour-service components
Properties and trade-offs
- Use laboratory or field data matching impurities and temperature.
- Assess crevices, deposits and aeration separately from bulk corrosion.
- Select weld filler and post-fabrication condition with the base alloy.
07
Fabrication, durability and inspection
Prevent iron and sulfur contamination.
Limit interpass temperature using a qualified welding procedure.
Use rigid machining and suitable tooling for work-hardening alloys.
08
Procurement checklist
- Provide stream composition, concentration, temperature and redox conditions.
- State UNS, product form, solution-annealed condition and code edition.
- Define PMI, corrosion testing, NDT and weld-consumable traceability.
09
Standards, sources and review
Standards and designation context
- UNS designation plus exact ASTM B-series product specification
- Applicable ASME construction code
- Qualified welding and heat-treatment procedure
Authoritative research sources
Nickel Institute · Technical overview, accessed 2026
Nickel Institute · Technical Guide 11012, revised edition
Nickel Institute · Technical Guide 393, 2021