Marine
Corrosion-Resistant Piping for Saltwater and Coastal Environments
316L and high-alloy stainless for vessel construction, offshore platforms, docks, marinas, and coastal infrastructure — where chloride-driven corrosion failure is not an acceptable outcome.
316 · 316L · 2205 · 254SMo
ASME B31.3 · ASTM A312 · A182 · DNV / Lloyd's Register material requirements
Sector Overview
Seawater Is One of the Most Corrosive Environments Your Piping Will Face
Seawater contains approximately 35,000 ppm chloride — enough to pit and crevice-corrode standard stainless grades in months under the wrong conditions. The marine environment adds intermittent wetting and drying in the splash zone, biofouling, and galvanic coupling risks between dissimilar metals. Material selection that ignores these conditions leads to early failure in applications where replacement is difficult and downtime is expensive.
Unified Alloys supplies stainless and high-alloy piping into marine and coastal applications throughout Canada, with particular strength on the West Coast through our Langley, BC branch. We stock 316L as the standard marine-grade specification and can supply 254SMo and duplex grades for permanently submerged, offshore, and high-chloride applications where 316L is insufficient.
All materials supplied with MTRs and full traceability documentation. Grade selection advice for specific marine service conditions is available from our technical sales team.
316/316L is the baseline specification for marine environments — its molybdenum content provides significantly better pitting resistance than 304 in chloride service. For permanently submerged or offshore applications, 254SMo (6% molybdenum) or duplex 2205 should be evaluated.
Facilities We Supply
- Commercial vessel and shipbuilding construction
- Offshore platform and marine structure piping
- Dock, marina, and port infrastructure
- Coastal industrial and processing facilities
- Desalination and seawater handling systems
- Aquaculture and marine processing operations
Chloride Pitting and Crevice Corrosion
Seawater chloride concentration causes pitting and crevice corrosion in stainless steels with insufficient pitting resistance equivalent (PREN). 316L (PREN ~24) is adequate for above-water and intermittent-contact marine applications. For permanently submerged or high-velocity seawater service, 254SMo (PREN ~43) or duplex 2205 (PREN ~35) provide substantially greater resistance.
Typical Grades
316L · 2205 · 254SMo
Splash Zone — Intermittent Wetting and Drying
The splash zone is more corrosively aggressive than permanent immersion because the wetting and drying cycle concentrates chlorides and accelerates pitting. 316L performs adequately in splash zone applications with appropriate design (minimising crevices); duplex grades are preferred for structural piping and fittings in high-exposure splash zone locations.
Typical Grades
316L · 2205
Biofouling and Microbiologically Influenced Corrosion
Marine environments support biofilm formation that creates localised corrosion cells — microbiologically influenced corrosion (MIC) — on stainless surfaces, particularly in stagnant or low-flow conditions. Smooth surface finish, appropriate flow velocities, and grade selection for the specific seawater chemistry all affect MIC risk.
Typical Grades
316L · 2205 · 254SMo
Galvanic Coupling
Stainless steel in contact with less noble metals — aluminium, mild steel, bronze — in a seawater electrolyte creates galvanic couples that accelerate corrosion of the less noble material. Proper isolation and material compatibility planning at the design stage prevents galvanic failures that are difficult to remediate once a vessel or structure is in service.
Typical Grades
316L (correct isolation practices required)
Desalination and Seawater Systems
Seawater handling and desalination systems — where seawater is the process fluid — require grades with PREN values sufficient to resist pitting in concentrated chloride at operating temperature. Duplex 2205 and 254SMo are the standard specifications; super-duplex 2507 is used in the most demanding seawater injection and high-temperature applications.
Typical Grades
2205 · 254SMo · 2507
Ready to Order or Need Help Sizing?
Our technical sales team can help you select the right size, material, and configuration for your application.