Titanium Grade 7 is a corrosion-resistant titanium grade based on Grade 2 commercially pure titanium with a small addition of palladium.
The palladium addition improves the stability of titanium’s passive oxide film and extends useful corrosion resistance into environments where unalloyed Grade 2 may be susceptible to attack.
Grade 7 is designated UNS R52400 and is often described nominally as Ti-0.2Pd.
Grade 7 Chemical Composition
| Element | Weight % |
|---|---|
| Titanium (Ti) | Balance |
| Palladium (Pd) | 0.12–0.25 |
| Oxygen (O) | ≤ 0.25 |
| Iron (Fe) | ≤ 0.30 |
| Carbon (C) | ≤ 0.08 |
| Nitrogen (N) | ≤ 0.03 |
| Hydrogen (H) | ≤ 0.015 |
The palladium content is therefore a specified range rather than exactly 0.15%.
Grade 7 Mechanical Properties
Grade 7 has mechanical properties broadly comparable with Grade 2. Representative minimum annealed values include:
| Property | Value |
|---|---|
| Ultimate tensile strength | ≥ 345 MPa |
| 0.2% yield strength | ≥ 275 MPa |
| Elongation | ≥ 20% |
| Density | approximately 4.51 g/cm³ |
Corrosion Resistance
The principal reason to select Grade 7 rather than Grade 2 is its enhanced corrosion performance.
Palladium promotes repassivation and improves resistance in a range of reducing acidic environments and aggressive chloride-containing conditions, particularly where crevice corrosion is a design concern.
Corrosion performance remains dependent on temperature, concentration, pH, contaminants and component geometry, so material selection should be based on the actual process environment.
Typical Applications
- Chemical-processing equipment
- Heat exchangers
- Piping and process vessels
- Acidic process streams
- Chloride and brine service
- Desalination equipment
- Condenser systems
- Equipment where Grade 2 corrosion resistance is insufficient
Common Specifications
- ASTM B265
- ASME SB-265
- Other ASTM/ASME titanium specifications covering Grade 7 tube, pipe, bar or forgings, as applicable
Technical Note
Chemical and mechanical properties shown are representative of commonly referenced specifications. Requirements can vary by product form, thickness, heat treatment and governing standard. Material should be ordered to the required specification, and the supplied material test report (MTR) should be used to verify compliance.
