Why Titanium Fasteners for Corrosive Environments
Standard steel fasteners, even stainless steel, can fail prematurely in aggressive chemical environments, marine applications, and high-temperature process systems. Titanium fasteners offer exceptional corrosion resistance combined with high strength-to-weight ratio, making them the material of choice for critical applications in chemical processing, offshore oil and gas, marine engineering, aerospace, and medical devices.
Titanium Fastener Grades
| Grade | Designation | Tensile Strength (MPa) | Key Properties | Best Application |
|---|---|---|---|---|
| Grade 2 (CP Ti) | UNS R50400 | 345 min | Excellent corrosion resistance, commercially pure | Chemical processing, marine |
| Grade 5 (Ti-6Al-4V) | UNS R56400 | 895 min | High strength, good corrosion resistance | Aerospace, high-stress applications |
| Grade 7 (CP Ti + 0.15% Pd) | UNS R52400 | 345 min | Enhanced crevice corrosion resistance | Hot chloride environments, sour gas |
| Grade 12 (Ti-0.3Mo-0.8Ni) | UNS R53400 | 483 min | Good strength + crevice corrosion resistance | Oil and gas, sour service |
| Grade 23 (Ti-6Al-4V ELI) | UNS R56407 | 860 min | Extra-low interstitial, improved fracture toughness | Medical implants, aerospace |
Corrosion Resistance by Environment
- Seawater: All titanium grades show zero corrosion rate in natural seawater. Immune to pitting, crevice corrosion, and stress corrosion cracking
- Chloride solutions: Grade 2 excellent up to 100 C; Grade 7/12 recommended above 100 C or in concentrated solutions
- Reducing acids (HCl, H2SO4): Titanium performs well in oxidizing conditions but can corrode in strongly reducing acids. Grade 7 with Pd addition extends the passive range
- Organic acids: Excellent resistance to acetic acid, citric acid, and most organic compounds
- Dry chlorine gas: Titanium can ignite in dry chlorine. Never use titanium in dry Cl2 service. Must have moisture present (greater than 1.5%)
- Hydrofluoric acid (HF): Titanium is NOT resistant to HF at any concentration – do not use
Galvanic Compatibility
When titanium fasteners are used with other materials, galvanic corrosion must be considered:
| Combination | Risk Level | Recommendation |
|---|---|---|
| Ti fastener + Ti structure | None | Preferred |
| Ti fastener + stainless steel structure | Low (Ti is cathodic) | Acceptable; SS structure may corrode slightly faster |
| Ti fastener + aluminum structure | HIGH (Al is anodic) | AVOID or use insulation sleeves/washers |
| Ti fastener + carbon steel structure | HIGH (CS is anodic) | AVOID or use full isolation |
| Steel fastener + Ti structure | HIGH (fastener corrodes) | NEVER use steel fasteners on titanium structure |
Fastener Types Available in Titanium
- Hex bolts: M3 to M64, hex head per ISO 4014/4017 or ASTM F468
- Stud bolts: M6 to M100, per ASME B16.5 or ASME B18.31.2
- Screws: Socket head cap screws, pan head, flat head per ISO 4762/10642
- Nuts: Hex nuts per ISO 4032, heavy hex per ASME B18.2.2
- Washers: Flat washers, spring washers, lock washers
Standards for Titanium Fasteners
- ASTM F468: Standard specification for nonferrous bolts, studs, and thread rods
- ASME B18.2.1: Dimensional standards for bolts and studs
- ISO 3506: Mechanical properties of corrosion-resistant fasteners (includes titanium)
- AMS 4910: Titanium alloy Ti-6Al-4V bar, forgings, and ring stock
Installation Considerations
- Galling prevention: Titanium is susceptible to galling (cold welding). Use anti-seize compound or silver-plated threads
- Torque values: Lower than steel fasteners due to lower modulus of elasticity. Use manufacturer-recommended torque tables
- Thread lubrication: Always lubricate titanium fastener threads before assembly
- Insulation: When mating with dissimilar metals, use insulating sleeves, washers, and coatings to prevent galvanic corrosion
- Storage: Keep separate from steel fasteners to avoid iron contamination, which can create corrosion sites
CoreMetal Steel: Titanium Fastener and Material Supply
CoreMetal Steel supplies titanium fasteners and raw materials in all standard grades:
- Grade 2 (CP Ti) hex bolts, studs, nuts, and washers
- Grade 5 (Ti-6Al-4V) high-strength fasteners for aerospace and structural
- Grade 7 and Grade 12 for enhanced corrosion resistance
- Titanium bar, rod, plate, and sheet for custom fastener manufacturing
- Full material certification per ASTM F468 or AMS specifications
Contact CoreMetal Steel for titanium fastener specifications, quantities, and pricing.