Benefits of Duplex Steel in Marine Hydraulic Applications
Why Duplex Stainless Steel Is Becoming the Preferred Choice for Offshore and Marine Hydraulic Systems
🌊 The Marine Environment: A Challenge for Hydraulic Systems
Hydraulic systems play a vital role in marine and offshore equipment—whether it’s for winches, cranes, steering gear, or deck lifts. However, the harsh saline environment, continuous moisture exposure, and extreme operating pressures demand materials with exceptional strength and corrosion resistance.
What Is Duplex Stainless Steel?
Duplex stainless steel is a family of grades combining the advantages of austenitic and ferritic structures. The result is a material with:
High strength (nearly twice that of 304/316)
Excellent corrosion resistance
Good weldability
High fatigue resistance
Common marine-grade duplex steels include UNS S31803 (2205) and UNS S32750 (Super Duplex 2507).
Key Benefits in Marine Hydraulic Applications
1. 🛡️ Superior Corrosion Resistance in Seawater
Duplex steel offers excellent resistance to:
Pitting and crevice corrosion
Chloride stress corrosion cracking (SCC)
General surface corrosion from salty environments
This makes it ideal for:
Hydraulic cylinder tubes
Piston rods
Manifolds
Connector fittings
2. ⚙️ High Mechanical Strength
With yield strength up to 450–550 MPa, duplex stainless reduces the wall thickness of cylinders or tubing while maintaining structural integrity. That means:
Lighter equipment
Lower material cost over time
More compact hydraulic systems
3. 🧊 Improved Fatigue and Pressure Resistance
Marine hydraulic systems often undergo:
High-frequency load cycles
Rapid pressure fluctuations
Duplex steel’s fatigue strength helps reduce the risk of:
Cracking
Deformation
Long-term system failure
4. 🛠️ Better Weldability and Machinability
Modern duplex steels are designed to offer:
Stable welding with minimal preheating
Good machinability for precision honed tubes, cylinder heads, and threaded fittings
JW Stainless, for example, supplies duplex honed tubes and rods that are already precision-machined and ready for direct cylinder assembly.
đź“Š Duplex Steel vs 316L in Marine Use
| Property | 316L Stainless Steel | Duplex 2205 |
| Yield Strength (MPa) | ~220 MPa | ~450 MPa |
| Pitting Resistance (PREN) | ~25 | ~35–40 |
| Chloride SCC Resistance | Moderate | Excellent |
| Fatigue Resistance | Good | Very Good |
| Cost | Lower | Slightly Higher, but cost-effective in long term |
âš“ Real-World Applications of Duplex in Marine Hydraulics
Offshore platforms: Jacking system cylinders, tensioners
Ship deck equipment: Winches, hatches, ramps
Subsea tools: Actuators, ROV manipulators
Marine cranes: High-load lifting cylinders
