Zr702 vs Zr705: Choosing the Right Zirconium Grade
Zr702 and Zr705 are the two most common wrought zirconium grades. One is unalloyed for maximum corrosion resistance; the other adds niobium for higher strength.
Use this article as an initial technical reference. Final material selection should also confirm grade, dimensions, tolerances, standards, quantity, and the actual service environment.
Zr702 and Zr705 are the two most common wrought zirconium grades. One is unalloyed for maximum corrosion resistance; the other adds niobium for higher strength.
What Zr702 and Zr705 are
Zr702 (UNS R60702) is commercially unalloyed zirconium. Zr705 (UNS R60705) is a zirconium-niobium alloy containing about 2–3% niobium. Both are prized for exceptional resistance to hydrochloric acid, most organic and inorganic acids, and chloride-containing media, and both are used in chemical processing, nuclear, and high-purity industrial systems.
The difference: strength vs. corrosion margin
The niobium addition makes Zr705 noticeably stronger than Zr702 while retaining excellent acid resistance. Zr702 offers the maximum corrosion margin and is the standard choice for nuclear fuel cladding because of its very low thermal neutron absorption cross-section. Zr705 is selected where a part needs higher strength together with corrosion resistance, such as shafts, pump components, and stressed reactor internals.
Comparison at a glance
| Property | Zr702 | Zr705 |
|---|---|---|
| UNS number | R60702 | R60705 |
| Alloying | Unalloyed | ~2–3% niobium |
| Strength | Moderate | Higher |
| Hydrochloric acid resistance | Excellent | Excellent |
| Nuclear fit | Primary | Selected |
Where each grade is used
- Zr702: nuclear fuel cladding, chemical reactors and liners, heat-exchanger parts, and low-stress corrosion service.
- Zr705: pump shafts, valve stems, fasteners, agitator parts, and reactor internals that combine acid service with mechanical load.
Zirconium should not be specified for fluoride-bearing media without a detailed corrosion review, since fluoride ions can attack zirconium.
Standards and how to specify
Zirconium rod and bar are typically supplied to ASTM B550 or B493, and sheet, strip, and plate to ASTM B551. When requesting a quote, state the grade (Zr702 or Zr705), UNS number, product form, dimensions, and the process environment.
FAQ
What is the main difference between Zr702 and Zr705?
Zr702 is unalloyed for maximum corrosion resistance; Zr705 adds niobium for higher strength while keeping strong hydrochloric acid resistance.
Is Zr705 as corrosion resistant as Zr702?
In most acid and chloride service the difference is small. Zr702 retains the highest corrosion margin; Zr705 is chosen when strength is also required.
Which grade is used in nuclear applications?
Zr702 is the primary nuclear grade because of its low thermal neutron cross-section; Zr705 is used in selected higher-strength nuclear and chemical parts.
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