Why Titanium for Marine Applications?
Titanium offers an unmatched combination of corrosion resistance, high strength-to-weight ratio, and long-term durability in marine environments. Unlike stainless steels, titanium is virtually immune to chloride-induced corrosion, including pitting, crevice corrosion, and stress corrosion cracking in seawater.
Titanium Grades for Marine Service
Grade 2 (CP Titanium / UNS R50400)
- Tensile strength: 345 MPa minimum
- Excellent seawater corrosion resistance — zero corrosion rate at ambient temperature
- Excellent formability and weldability
- Best for: Heat exchanger tubes, condenser plates, desalination components, marine piping
Grade 5 (Ti-6Al-4V / UNS R56400)
- Tensile strength: 895 MPa minimum
- Nearly double the strength of Grade 2
- Good seawater corrosion resistance
- Best for: Submarine hull components, offshore risers, high-strength fasteners, propulsion shafts
Grade 7 (Ti-0.15Pd / UNS R52400)
- Same mechanical properties as Grade 2
- Enhanced crevice corrosion resistance from palladium addition
- Best for: Heat exchangers in hot seawater (>80°C), acid cleaning environments
Grade 12 (Ti-0.3Mo-0.8Ni / UNS R53400)
- Tensile strength: 483 MPa minimum
- Higher strength than Grade 2, with similar corrosion resistance
- Excellent crevice corrosion resistance
- Best for: Heat exchanger tubes, desalination plant components, marine piping
Grade 19 (Ti-6Al-4V-0.06Pd / UNS R55619)
- Same high strength as Grade 5 with enhanced crevice corrosion resistance
- Best for: Offshore oil and gas, deepwater risers, high-pressure manifolds
Grade 29 (Ti-6Al-4V ELI / UNS R56406)
- Extra Low Interstitial content for higher fracture toughness
- Excellent seawater corrosion resistance
- Best for: Submarine components, arctic offshore risers, fatigue-critical structures
Grade Selection Comparison
| Grade | Yield (MPa) | Tensile (MPa) | Crevice Corr. | Relative Cost |
|---|---|---|---|---|
| Grade 2 (CP) | 275 | 345 | Excellent | 1.0× |
| Grade 5 (Ti-6Al-4V) | 830 | 895 | Good | 1.3× |
| Grade 7 (Ti-0.15Pd) | 275 | 345 | Superior | 2.0× |
| Grade 12 | 345 | 483 | Excellent | 1.4× |
| Grade 19 | 830 | 895 | Superior | 2.5× |
| Grade 29 (ELI) | 795 | 860 | Excellent | 1.8× |
Corrosion Resistance in Seawater
- General corrosion: Essentially zero (<0.001 mm/year)
- Pitting: Immune in natural seawater at all temperatures
- Crevice corrosion: CP grades (2, 7, 12) excellent. Grade 5 can crevice corrode in hot (>80°C) seawater. Pd-modified grades (7, 19) eliminate this risk.
- Stress corrosion cracking: Immune to chloride SCC
- Galvanic compatibility: Titanium is the most noble metal — coupling accelerates corrosion of less noble metals
Design Considerations
- Galvanic isolation: Always isolate titanium from less noble metals
- Hydrogen embrittlement: Limit CP potential: -0.9V vs Ag/AgCl for Grade 2; -0.7V for Grade 5
- Crevice design: Minimize tight crevices in Grade 5 for hot seawater. Use Grade 12 or Grade 7 if unavoidable.
- Fretting: Use dissimilar metal inserts or surface treatments at contact points
Standards for Marine Titanium
- ASTM B265: Titanium strip, sheet, and plate
- ASTM B338: Titanium tubes for condensers and heat exchangers
- ASTM B861: Seamless titanium pipe
- NACE MR0175/ISO 15156: Materials for sour service
- DNV-RP-F113: Titanium risers for offshore applications
CoreMetal Steel — Marine-Grade Titanium Products
CoreMetal Steel supplies titanium products for marine and offshore applications. We stock Grade 2, Grade 5, Grade 7, and Grade 12 in tube, pipe, plate, sheet, bar, and fittings. All products comply with ASTM, ASME, and DNV standards.
Email: tracy@coremetalsteel.com | Phone: +86 18291910632