ASTM F594
Group 2
AISI 316 / 316L Nuts
Why the Nut Needs the Same Chemistry as the Bolt
ASTM F593 and ASTM F594 are companion specifications — F593 governs externally threaded stainless fasteners, while F594 governs the matching internally threaded nuts, both organized into the same alloy group system so a Group 2 bolt and Group 2 nut are guaranteed to be metallurgically matched and dimensionally compatible.
Pairing a Group 2 molybdenum-bearing bolt with a Group 1 nut lacking molybdenum would genuinely undermine the point of specifying 316 in the first place — thread engagement and crevice areas within a nut are precisely the kind of stagnant, chloride-concentrating geometry where pitting and crevice corrosion initiate, so a nut without molybdenum’s added resistance can become the weak point in an otherwise chloride-resistant assembly, regardless of how well the bolt itself resists corrosion.
F594 Group 2 supplies that matching nickel-chromium-molybdenum chemistry specifically for the nut half of the joint — the same alloy content, same corrosion mechanism, and same 316L low-carbon option for weld-adjacent applications, ensuring the entire fastened connection carries consistent chloride resistance rather than only half of it.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our ASTM F594 Group 2 nut range is manufactured and verified by chemical composition and mechanical testing under our ISO 9001:2015 quality system.
A Note on Matched Assemblies
We strongly recommend ordering F593 Group 2 bolts/studs and F594 Group 2 nuts together as a matched set, since a mismatched nut can genuinely compromise the corrosion resistance the bolt was specified to provide. Let us know if you’d like both quoted together.
Where This Material Genuinely Applies
Genuine Chloride & Pitting Resistance
Molybdenum content resists corrosion specifically in stagnant thread and crevice geometry.
Guaranteed Bolt Compatibility
Matched alloy group system ensures dimensional and metallurgical compatibility with F593 bolts.
316L Weld-Decay Protection
Low carbon content genuinely reduces sensitization risk near welded assemblies.
Verified Mechanical Properties
Batch testing confirms genuine alloy content and mechanical properties for every lot.
F594 Group 2 vs Group 1 — Quick Reference
Confirming whether chloride exposure is a genuine operating condition before paying for the added molybdenum. This table is the quick reference we use with buyers before quoting.
| Aspect | F594 Group 2 (316/316L) | F594 Group 1 (304/304L) |
|---|---|---|
| Molybdenum Content | ~2 – 3% | None |
| Chloride/Pitting Resistance | Genuinely superior | Good, general exposure only |
| Matching Bolt Standard | ASTM F593 Group 2 | ASTM F593 Group 1 |
| Best Suited For | Marine, coastal, chloride-heavy chemical service | General atmospheric, food, mild chemical |
F594 Group 2 Specification Details
Nominal Composition
- Chromium 16.0 – 18.0%
- Nickel 10.0 – 14.0%
- Molybdenum 2.0 – 3.0%
- Carbon (316L) ≤0.03%
Typical Mechanical Range
- Condition Cold Worked / Annealed
- Chloride/Pitting Resistance Genuinely Superior to Group 1
- Matching Bolt Standard ASTM F593 Group 2
- Fastener Standard ASTM F594 Group 2
Fastener Types We Manufacture
- Hex Nuts Standard & Heavy Hex
- Jam Nuts Thin Profile
- Matching Bolts & Studs ASTM F593, On Request
- Washers Matching Material
Application Areas
Wherever chloride exposure — marine, coastal, or chemical — genuinely drives the material selection beyond Group 1’s capability.
Marine & Offshore Hardware
spray exposure fastening
Coastal Architectural & Structural
infrastructure fastening
Chemical & Pharmaceutical Processing
stream equipment fastening
Desalination & Water Treatment
water equipment fastening
Standard Export Documentation
Prepared as standard practice for every ASTM F594 Group 2 nut shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Chemical Composition Report
Confirms actual chromium, nickel, molybdenum, and carbon content fall within the specified 316/316L range.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/size specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical and dimensional testing available on request.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
ASTM F593 Group 2 (316/316L)
Our companion bolt, hex cap screw, and stud specification, for a complete matched Group 2 assembly.
View F593 Group 2 →ASTM F594 Group 1 (304/304L)
Our general-purpose nut grade, sufficient where chloride exposure is not a driving concern.
View F594 Group 1 →UNS C71500 Cupro-Nickel 70/30
Our copper-nickel alloy, an alternative non-ferrous option for high-velocity seawater erosion service.
View UNS C71500 →Stainless Steel Fasteners Manufacturer India
Our broader fastener manufacturing capability across all major carbon, alloy, stainless, and non-ferrous grades.
View SS Manufacturer Guide →Need Matching Nuts
for Your F593 Group 2 Bolts?
Tell us your application and chloride exposure level — we’ll confirm whether 316 or 316L fits, and quote your complete matched bolt-and-nut assembly with full documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in