Nickel alloy · Ni-Cr-Mo-W · UNS N06022 · W.Nr. 2.4602
Hastelloy C22: more chromium for oxidising and mixed acids
In short: Hastelloy C22 is a nickel-chromium-molybdenum-tungsten alloy that carries more chromium than C276 (20–22.5%), trading a little molybdenum for better resistance to oxidising media. It is chosen for process streams that contain oxidisers such as chlorine or ferric and cupric ions, or that swing between oxidising and reducing.
Overview
Hastelloy C22 in brief
- Resists both oxidising and reducing media
- PREN about 65–70
- Excellent resistance to wet chlorine and hypochlorite
- Resists weld heat-affected-zone precipitation
With about 22% chromium, 13% molybdenum and 3% tungsten, Alloy C22 has more chromium than C276. That improves its resistance to oxidising acids, ferric and cupric chlorides and wet chlorine while keeping excellent resistance to reducing media. It's often chosen where process streams switch between oxidising and reducing conditions.
Applications include pharmaceutical and agrochemical reactors, chlorination systems, pickling and pulp bleach plants, FGD systems and waste incineration. Its weld filler (ERNiCrMo-10) is also used to join other corrosion-resistant alloys.
Available as
Hastelloy C22 product forms
Select a form for its specification, sizes and weights.
Where it's used
Industries that specify Hastelloy C22
Selection
C22 or C276: start with the oxidisers
| Process condition | Usually favours |
|---|---|
| Oxidising species present (chlorine, ferric or cupric ions, nitric) | C22 |
| Strongly reducing acids (hot hydrochloric, sulphuric) | C276 |
| Streams that alternate between oxidising and reducing | C22 |
| Welding filler to protect other Ni-Cr-Mo alloys | C22-type filler |
Guidance only. Corrosion testing in the actual process stream decides.
Chemistry
Composition of Hastelloy C22
- UNS
- N06022
- EN / W.Nr.
- 2.4602 · NiCr21Mo14W
- Density
- 8.69 g/cm³
- PREN
- ≈ 65 – 70
| Element | Limit, % | Why it matters |
|---|---|---|
| Ni | Balance | |
| Cr | 20.0 – 22.5 | 20–22.5%: oxidising media |
| Mo | 12.5 – 14.5 | 12.5–14.5%: reducing acids |
| W | 2.5 – 3.5 | 2.5–3.5% |
| Fe | 2.0 – 6.0 | |
| Co | 2.5 max | |
| C | 0.015 max | |
| Si | 0.08 max | |
| Mn | 0.50 max | |
| V | 0.35 max |
Limits per ASTM B575; other product forms and specifications differ slightly. Your order's specification and edition govern.
Mechanical properties
Solution-annealed room-temperature values
ASTM B575 (solution-annealed): room-temperature specification values for the annealed condition.
Supply
C22 by product form
| Product form | Specification and designation |
|---|---|
| Hastelloy C22 pipes | ASTM B622 (seamless) / B619 (welded) |
| Hastelloy C22 tubes | ASTM B622 / B626 |
| Hastelloy C22 plates | ASTM B575 / ASME SB575 |
| Hastelloy C22 sheets | ASTM B575 |
| Hastelloy C22 coils | ASTM B575 |
| Hastelloy C22 bars | ASTM B574 / ASME SB574 |
| Hastelloy C22 fittings | ASTM B366 WPHC22 |
| Hastelloy C22 flanges | ASTM B564 N06022 |
| Hastelloy C22 bolts | ASTM B574 bar stock |
| Hastelloy C22 nuts | ASTM B574 |
| Hastelloy C22 washers | ASTM B575 |
- Product specification per form (B622, B575, B574, B564)
- Oxidising species in the process stream
- Solution-annealed condition
- Filler type (C22-type is common)
- Surface finish for pharmaceutical service
Ordering
What to put on an order for Hastelloy C22
Getting these on the enquiry avoids the usual back-and-forth and makes sure the certificate matches your specification.
C22 questions
Answers about Hastelloy C22
- What is the difference between Hastelloy C22 and C276?
C22 has more chromium (20–22.5% against 14.5–16.5%) and somewhat less molybdenum and tungsten. Haynes describes the higher chromium as giving C22 better resistance to oxidising media.[1] C276 remains strong in highly reducing acids. Compare C276 vs C22.
- Where is Hastelloy C22 used?
Pharmaceutical and fine-chemical reactors, chlorination and bleaching systems, acid pickling, flue-gas desulphurisation, and waste incineration and scrubbing: environments with oxidising species, or that swing between oxidising and reducing.
- Is C22 used as a weld filler for other alloys?
Yes. C22-type filler is often used to weld other Ni-Cr-Mo alloys and to overlay corrosion-prone areas, because its balanced chromium and molybdenum resist a broad range of conditions.
Sources
References
Hastelloy® is a trademark of Haynes International. Composition per the cited specification.
Need Hastelloy C22?
Send form, size and the process chemistry, especially any oxidising species.