Marine hardware faces a unique combination of challenges: constant salt spray, UV radiation, thermal cycling, and mechanical stress from wave action. Selecting the right stainless steel grade is the single most important material decision for any marine fastener, fitting, or structural component.
Three Grades Every Marine Professional Should Know
Three stainless steel grades dominate marine applications — each with distinct performance characteristics and cost profiles.
| Grade | Key Composition | Marine Suitability | Typical Applications |
|---|---|---|---|
| SS304 | 18% Cr, 8% Ni | Inland / freshwater only | Indoor, coastal indoor storage |
| SS316 / 316L | 16% Cr, 10% Ni, 2–3% Mo | All marine environments | Leisure boats, yachts, chandleries |
| Duplex 2205 | 22% Cr, 5% Ni, 3% Mo | Commercial & offshore | Workboats, commercial vessels, offshore platforms |
SS304: When It's Acceptable — and When It's Not
SS304 is a versatile general-purpose stainless steel with good corrosion resistance in normal atmospheric conditions. However, it lacks sufficient chloride resistance for sustained marine use. SS304 is acceptable in:
- Freshwater environments (lakes, rivers)
- Indoor marine equipment storage
- Above-deck hardware on boats used exclusively in inland waterways
It is not suitable for: coastal environments, salt water exposure, underwater fittings, or any application where salt spray is unavoidable.
SS316 / 316L: The Industry Standard
SS316 and its low-carbon variant SS316L are the standard for leisure marine hardware worldwide. The addition of 2–3% molybdenum provides excellent resistance to:
- Pitting corrosion in salt water
- Crevice corrosion under biofilm deposits
- Stress corrosion cracking under thermal stress
SS316L (low carbon) is preferred for welded fabrications as the lower carbon content (≤0.03%) prevents sensitisation — the precipitation of chromium carbides at grain boundaries that weakens corrosion resistance in the heat-affected zone.
Duplex 2205: For Demanding Commercial Applications
Duplex 2205 is a two-phase stainless steel combining austenitic and ferritic microstructure. It offers nearly twice the yield strength of SS316 and superior corrosion resistance, making it ideal for:
- Commercial workboat hardware under high mechanical load
- Offshore platform fittings exposed to constant salt spray
- Large superyacht custom builds with weight constraints (higher strength = less material needed)
The trade-off is cost — Duplex 2205 is approximately 2–3× the price of SS316 and requires more precise manufacturing processes.
SNOWL's Product Grade Summary
📋 SNOWL Material Guide
- OWOZ Series, Snap Fasteners, Turn Buttons, Nylon Buttons (retail): SS316L as standard — ideal for all leisure marine applications.
- OEM / Bulk Orders: SS316L standard; Duplex 2205 available on request for commercial projects.
- SS304: Not offered for marine applications. We do not compromise on material grade.
"The right stainless steel grade for a marine fastener is the one that outlasts the boat. SS316L consistently delivers that for leisure marine — it's the right balance of performance and cost." — SNOWL Engineering Team
SS316L Marine Hardware from SNOWL
All SNOWL retail marine hardware is manufactured in SS316L. Explore our product range and request samples for your next marine project.
View Products →Article published December 2025. Material specifications sourced from ASTM A240 and EN 10088 standards. SNOWL is a marine fastener manufacturer based in Hong Kong, established 1995.