Alloy Overview
ASTM Grade 7 Titanium (Ti-Pd Alloy, UNS R52400) is a corrosion-resistant titanium alloy with 0.12–0.25% palladium (Pd) added to unalloyed titanium. It is recognized as the most corrosion-resistant among available titanium alloys, excelling in resisting general and localized crevice corrosion—especially in reducing environments where pure titanium may struggle to form a protective oxide film.
Beta Transus Temperature: 1675°F ± 25°F (≈913°C ± 14°C)
Chemical Composition (Nominal, wt%)
| Element | Content Range |
| Ti | Balance |
| Pd | 0.12–0.25 |
| C | ≤0.08 (Max) |
| O | ≤0.25 (Max) |
| N | ≤0.03 (Max) |
| Fe | ≤0.3 (Max) |
| H | ≤0.015 (Max) |
Mechanical Properties
| Property | Minimum Value |
| Tensile Strength | 345 MPa |
| Yield Strength (0.2%) | 275 MPa |
| Elongation | 20% |
| Reduction of Area | 30% |
Key Features
- Corrosion Resistance: Exceptional in both oxidizing and reducing environments (e.g., reducing acids). The addition of Pd enhances oxide film formation in slightly reducing conditions, outperforming pure titanium.
- Mechanical Traits: Equivalent to CP3 (Grade 3) or Grade 2 titanium in physical and mechanical properties; maintains formability while boosting corrosion resistance.
- Fabrication: Excellent weldability and fabricability, compatible with standard titanium processing methods (welding, machining, forging).
Applications
Widely used in industries demanding high corrosion resistance:
- Chemical processing (handling reducing acids, corrosive chemicals).
- Pharmaceutical manufacturing, desalination, and marine environments.
- Equipment like seamless/welded pipes, tubes, sheets, plates, forgings, fittings, and valves.
Specifications & Standards
| Product Form | ASME Specification |
| Sheet/Plate | ASME SB-265 |
| Bar/Wire | ASME SB-348 |
| Pipe/Tube | ASME SB-337, ASME SB-338 |
| Fittings | ASME SB-363 |
| Forgings | ASME SB-381 |
Comparison with Similar Grades
Grade 7 is part of a family of corrosion-resistant titanium alloys (including Grades 11, 16, 17) where mechanical properties and cost are determined by palladium content. It offers a balance of corrosion resistance and affordability for reducing-environment applications.