Hastelloy C22
Fasteners
UNS N06022
Hastelloy C22 — Highest Cr in Ni-Cr-Mo Family · PRE≈73
Hastelloy C22 (UNS N06022) is a Ni-Cr-Mo-W alloy with 20–22.5% chromium — the highest Cr content in the commercial Ni-Cr-Mo alloy family, higher than C276 (14.5–16.5% Cr) and higher than C4. The increased chromium raises the Pitting Resistance Equivalent (PRE≈73) well above C276 (PRE≈66) and far above 316L (PRE≈24). This elevated PRE makes C22 the preferred alloy for the most aggressive oxidising chloride environments: flue gas desulphurisation (FGD) absorber vessels, wet chlorine scrubbers, hypochlorite processing, and seawater with added oxidising agents.
The engineering tradeoff: C22’s higher Cr gives it superior oxidising acid and oxidising chloride resistance over C276, but its lower Mo (12.5–14.5% vs C276’s 15–17%) gives it slightly lower resistance to reducing acids like HCl. For mixed or undefined acid media — where process fluid varies or is not precisely characterised — C276 remains the correct default. For specifically oxidising chloride service (FGD, bleach, wet Cl₂, hypochlorite), C22 is the technically superior and correct choice.
The ultra-low carbon (≤0.015%) prevents sensitisation at weld HAZ. W (2.5–3.5%) supplements Mo in reducing pitting and crevice corrosion specifically in reducing chloride environments. All C22 fasteners from Akbar Fasteners are manufactured from ASTM B574 certified UNS N06022 solution-annealed bar, XRF PMI-verified before production. Matched C22 heavy hex nuts and Hastelloy washers from same heat on request.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel (Ni) | Balance | — | ~56% |
| Chromium (Cr) | 20.0 | 22.5 | ~22% |
| Molybdenum (Mo) | 12.5 | 14.5 | ~13.5% |
| Tungsten (W) | 2.5 | 3.5 | ~3% |
| Iron (Fe) | 2.0 | 6.0 | ~4% |
| Cobalt (Co) | — | 2.5 | — |
| Vanadium (V) | — | 0.35 | — |
| Carbon (C) | — | 0.015 | — |
Hastelloy C22 Fasteners — All Product Forms
All product forms machined from ASTM B574 certified UNS N06022 solution-annealed bar. PMI-verified before production. Matched sets from same heat — one MTC, one PMI, one COC for the complete assembly.
C22 Stud Bolts
Fully threaded and double-end. Class 150–2500, M12–M100, lengths to 3,000mm. Primary C22 fastener for ASME B16.5 pressure flanges in FGD absorbers, wet chlorine scrubbers, and oxidising chloride process equipment.
View Stud Bolts →C22 Hex Bolts
Full thread, partial thread, heavy hex, socket cap. M6–M100. FGD ductwork bolts, bleach plant equipment covers, hypochlorite reactor body connections, and chlorinated seawater system bolting.
View Hex Bolts →C22 Hex Nuts
Standard hex, heavy hex, coupling nuts. M6–M100. Matched from same ASTM B574 certified heat as stud bolts — zero galvanic risk at the nut bearing face in FGD, bleach, and oxidising chloride service.
Enquire →Hastelloy Washers
Plain flat, spring, and large OD washers in C22 and C276 from same certified heat as stud bolts. M5–M100. Matched-alloy assembly for zero galvanic corrosion at the washer-nut bearing face in oxidising chloride service.
View Washers →C22 Threaded Rods
Full thread and end-thread. M6–M100, lengths to 3,000mm. FGD absorber hanger systems, bleach plant tie-rods, and chlorinated chemical plant structural rods in oxidising chloride environments.
Enquire →Socket Cap Screws
Hex socket cylindrical head for confined-access FGD and bleach plant bolting. M4–M36. Internal fixtures in chlorine scrubbers, instrument flange connections, and hypochlorite equipment where hex head clearance is unavailable.
View Bolts →Matched Assembly Sets
C22 stud bolts + heavy hex nuts + washers from same certified UNS N06022 heat. One MTC, one PMI, one COC for the complete flange assembly — simplified TPI hold plan for FGD and bleach plant EPC projects.
Request Matched Set →Custom / ASTM B574
Non-standard diameters, inch UNC/UNF thread, drawing-specific head forms, and C22 alongside the full ASTM B574 C-series range. Contact sales@akbarfasteners.in with your specification.
View ASTM B574 →Hastelloy C22 vs C276 — Corrosion Environment Selection
C22 and C276 share the same Ni-Cr-Mo-W alloy family. C22’s higher Cr (22%) gives superior oxidising chloride resistance; C276’s higher Mo (16%) gives superior reducing acid and mixed media resistance. Use this matrix to select the correct grade — both available from Akbar Fasteners in all product forms.
| Corrosion Environment | C22 (N06022) This Page | C276 (N10276) |
|---|---|---|
| FGD Absorber Service (wet SO₂ + Cl⁻) | ✔ Best Choice | Good |
| Oxidising Chloride / Seawater + Oxidiser | ✔ Best Choice | Good |
| Hypochlorite / Bleach Solutions | ✔ Best Choice | Good |
| Wet Chlorine Gas (Cl₂) | ✔ Best Choice | Good |
| Oxidising Acids (HNO₃, HClO₄) | ✔ Best Choice | Good |
| Mixed / Variable / Unknown Acids | Limited — use C276 | ✔ Best Choice |
| Reducing HCl (all concentrations) | Poor — use B3 | Moderate |
| Dilute H₂SO₄ (reducing) | Moderate | Good |
| Chlorinated Solvents / Wet Cl₂ | Good | ✔ Best Choice |
| Seawater (no oxidising agents) | ✔ Excellent — PRE≈73 | Excellent — PRE≈66 |
| NACE H₂S Sour Service | ✔ Compliant ≤241 HB | ✔ Compliant ≤241 HB |
| Phosphoric Acid (H₃PO₄) | Good | ✔ Better |
Grade selection help: C276 Fasteners · B3 for HCl · Full Hastelloy Range
Standards We Manufacture & Test To
Same quality system as our Hastelloy B3 stud bolts and complete ASTM B574 Hastelloy fastener range. Full heat traceability from mill certificate to dispatch.
Industry Applications
Oxidising chloride and FGD environments where C276 is adequate but C22’s PRE≈73 provides an additional safety margin — or where FGD project specification specifically calls for C22.
FGD Absorbers
duct work connections
Bleach / Hypochlorite
hypochlorite reactor bolts
Offshore Seawater
chlorinated injection systems
Oil & Gas
oxidising chloride flanges
Pulp & Paper
oxidising bleaching flanges
Desalination
oxidising media flanges
Pharmaceutical
chlorine CIP systems
Waste Treatment
wet scrubber connections
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Related Hastelloy Fasteners
C22 for FGD and oxidising chloride. C276 for mixed media. B3 for reducing HCl. All from one certified Mumbai facility.
Hastelloy C22 Stud Bolts
C22 fully threaded stud bolts for ASME B16.5 FGD and oxidising chloride pressure flanges. Class 150–2500, M12–M100, lengths to 3,000mm. Matched heavy hex nuts from same heat.
View Page →Hastelloy C276 Fasteners
For mixed or undefined acid media — C276’s higher Mo gives broader dual-media coverage. PRE≈66. When the corrosion environment is mixed or variable, C276 is the correct default over C22.
View Page →Hastelloy B3 Stud Bolts
For reducing HCl service — where C22 and C276 both show limited resistance. B3’s 28% Mo without Cr gives near-zero corrosion in HCl at all concentrations.
View Page →Hastelloy Fasteners India
Complete Hastelloy range — six grades, all product forms, grade selection guidance. ISO 9001:2015 certified Mumbai facility. Export to 50+ countries.
View Full Range →Need Hastelloy C22
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