Hastelloy C276
Washers
UNS N10276
C276 Washers — Completing the Matched Assembly
In mixed acid, chlorinated solvent, and multi-fluid process environments where Hastelloy C276 stud bolts and bolts are specified, using a dissimilar washer material creates a galvanic couple at the most vulnerable point in the bolted joint — the washer-to-nut bearing face, where the electrolyte pools in crevice geometry. A 316L washer under a C276 nut will corrode preferentially in mixed acid service, reducing bearing area and clamping load within months.
Using matched UNS N10276 Hastelloy C276 washers eliminates this failure path. Same alloy throughout — no electrochemical potential difference, no galvanic couple, no crevice attack under the washer face in any of the mixed media environments where C276 is specified. Akbar Fasteners Pvt. Ltd. supplies C276 washers from the same ASTM B574 certified heat as the matching stud bolts and bolts — one mill test certificate and one PMI report covering the complete fastener assembly, simplifying vendor document submission.
For C276 stud bolt sets in ASME B16.5 pressure flange assemblies, the complete matched set — stud bolts, heavy hex nuts, and washers — from the same certified heat is available on request. Compared with our Hastelloy B3 washers for reducing acid service and C22 matched sets for oxidising chloride service.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel (Ni) | Balance | — | ~57% |
| Molybdenum (Mo) | 15.0 | 17.0 | ~16% |
| Chromium (Cr) | 14.5 | 16.5 | ~15.5% |
| Tungsten (W) | 3.0 | 4.5 | ~4% |
| Iron (Fe) | 4.0 | 7.0 | ~5.5% |
| Cobalt (Co) | — | 2.5 | — |
| Manganese (Mn) | — | 1.0 | — |
| Carbon (C) | — | 0.010 | — |
| Silicon (Si) | — | 0.08 | — |
| Vanadium (V) | — | 0.35 | — |
Why C276 Washers with C276 Bolts
The mixed acid and chlorinated process environments where Hastelloy C276 is specified are exactly the environments where washer material selection is most critical. A dissimilar washer creates a localised corrosion problem at the bearing face — the point in the assembly where the nut generates maximum contact stress against the washer and where electrolyte accumulates in the crevice.
The four specific failure modes below — each one uniquely relevant to C276 service environments — explain why Akbar Fasteners Pvt. Ltd. supplies C276 washers from the same certified heat as the matching fasteners, and why project engineers specify the complete matched assembly in TPI hold plans and vendor document packages.
Zero Galvanic Corrosion at Bearing Face
C276 washer under a C276 nut — identical alloy, zero electrochemical potential difference. No galvanic cell at the bearing interface in any of C276’s mixed acid or chlorinated solvent service environments.
No Crevice Attack Under Washer
C276’s 16% Mo gives outstanding crevice corrosion resistance in the stagnant electrolyte trapped under the washer bearing face — the most critical crevice geometry in a bolted chemical plant flange joint.
Maintained Bolt Preload in Service
A corroding washer loses thickness over time, reducing bolt preload and eventually causing flange leakage. A matched C276 washer maintains dimensional integrity throughout service life in mixed acid environments.
Single MTC Covers Complete Assembly
Stud bolt, nut, and washer from the same UNS N10276 certified heat — one mill test certificate, one PMI report, one COC covering the full assembly. Simplifies TPI hold plan documentation and vendor document submission for EPC projects.
Hastelloy C276 Washer Types & Standards
All types machined from ASTM B574 certified UNS N10276 solution-annealed sheet or bar. PMI-verified before production. Full MTC and COC on every order.
Plain Flat Washers
Standard flat washers in Hastelloy C276 to DIN 125A and DIN 125B / ISO 7089 — distributes bolt load over a greater bearing area and provides a corrosion-matched contact surface under the nut in mixed acid and chlorinated solvent service. Series A (tight ID) and Series B (clearance ID). M5–M100. Standard stock for common sizes M5–M48.
Spring Washers
Split-ring (helical) spring washers in C276 to DIN 127 — maintain bolt preload against vibration and thermal cycling in chemical plant equipment with pump-induced vibration, rotating agitators, and pulsating pressure. M5–M64. Critical in chemical reactor covers and heat exchanger heads subject to thermal cycling in corrosive mixed media.
Large OD Washers
Extra-large outer diameter washers in C276 for chemical plant structural connections through composite materials, non-metallic lining, and soft substrates in corrosive environments where a standard OD washer would pull through. Used in FRP-lined vessel nozzle connections, rubber-lined equipment covers, and chemical plant structural supports in mixed acid environments. M6–M64.
Custom Profile Washers
Non-standard OD/ID combinations, reduced thickness, and square washers machined from C276 sheet for specialised chemical process equipment requiring specific bearing area calculations or custom flange geometry. Send drawing to sales@akbarfasteners.in. Inch sizes and SAE washer types available.
DIN 125 C276 Flat Washer Dimensions
Standard dimensions per DIN 125 / ISO 7089. All in mm. DIN 127 spring washer and large OD dimensions on request to sales@akbarfasteners.in.
| Bolt Size (M) | Washer ID (d1) mm | Std OD (d2) mm | Large OD (d2) mm | Thickness (h) mm | Standard | Material | Condition |
|---|---|---|---|---|---|---|---|
| DIN 125 / ISO 7089 — PLAIN FLAT WASHERS (UNS N10276 · ASTM B574 · SOL. ANNEALED) | |||||||
| M5 | 5.3 | 10 | 15 | 1.0 | DIN 125A | N10276 | Sol. Ann. |
| M6 | 6.4 | 12 | 18 | 1.6 | DIN 125A | N10276 | Sol. Ann. |
| M8 | 8.4 | 16 | 24 | 1.6 | DIN 125A | N10276 | Sol. Ann. |
| M10 | 10.5 | 20 | 30 | 2.0 | DIN 125A | N10276 | Sol. Ann. |
| M12 | 13.0 | 24 | 37 | 2.5 | DIN 125A | N10276 | Sol. Ann. |
| M16 | 17.0 | 30 | 44 | 3.0 | DIN 125A | N10276 | Sol. Ann. |
| M20 | 21.0 | 37 | 60 | 3.0 | DIN 125A | N10276 | Sol. Ann. |
| M24 | 25.0 | 44 | 72 | 4.0 | DIN 125B | N10276 | Sol. Ann. |
| M30 | 31.0 | 56 | 92 | 4.0 | DIN 125B | N10276 | Sol. Ann. |
| M36 | 37.0 | 66 | 110 | 5.0 | DIN 125B | N10276 | Sol. Ann. |
| M42 | 45.0 | 78 | Custom | 7.0 | DIN 125B | N10276 | Sol. Ann. |
| M48 | 52.0 | 92 | Custom | 8.0 | DIN 125B | N10276 | Sol. Ann. |
| M56 – M100 | Custom | Custom | Custom | Custom | Custom | N10276 | Sol. Ann. |
* DIN 127 spring, SAE flat, inch sizes, and non-standard OD/ID to drawing — sales@akbarfasteners.in
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
Wherever C276 bolts and stud bolts are specified — the washer must be C276 too. These are the mixed-media service environments that require the complete matched alloy assembly.
Chemical Plant Flanges
complete matched assembly
FGD Scrubbers
absorber nozzle assemblies
Oil & Gas
offshore mixed media
Offshore Platforms
seawater + acid service
Pulp & Paper
mixed acid recovery
Pharmaceutical
CIP system assemblies
Desalination
brine circuit assemblies
Waste Treatment
scrubber body assemblies
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Matched C276 Fastener Components
Order washers with stud bolts and nuts from the same certified UNS N10276 heat — one MTC, one PMI, zero galvanic risk throughout the assembly.
Hastelloy C276 Stud Bolts
Fully threaded and double-end stud bolts, Class 150–2500, M12–M100 to 3,000mm. Supply with these matching C276 washers and heavy hex nuts from same certified heat.
View Page →ASTM B574 Hastelloy Fasteners
Full C276 range — hex bolts, hex nuts, stud bolts, threaded rods. Grade selection matrix across C-series and B-series alloys for your service environment.
View All Grades →Hastelloy B3 Washers
Matched washers for Hastelloy B3 stud bolt sets in reducing HCl and H₂SO₄ service. Same matched-material principle applied to B3 fastener assemblies.
View Page →Hastelloy B3 Stud Bolts
For reducing HCl and strongly reducing acid service where B3 outperforms C276. Near-zero corrosion in HCl at all concentrations. Class 150–2500, M12–M100.
View Page →Need Hastelloy C276
Washers Now?
Type · bolt size · quantity · matched set requirement. Akbar Fasteners Pvt. Ltd. responds within 24 hours with full pricing and documentation list.