Titanium Grade 7 is a commercially pure titanium alloy enhanced with a small addition of palladium, engineered specifically for exceptional corrosion resistance.
It retains the excellent formability and weldability of Titanium Grade 2 while delivering dramatically improved resistance to reducing acids and crevice corrosion, making it one of the most corrosion-resistant titanium grades available.
Alloy Identification
| Standard | Designation |
|---|---|
| UNS | R52400 |
| ASTM | B265, B348, B381 |
| Alloy Type | CP Titanium + Palladium (Alpha Titanium) |
| Strength Level | Similar to Grade 2 |
| Key Feature | Exceptional corrosion resistance |
Metallurgical Behavior & Strengthening
Titanium Grade 7 is not heat-treatable. Strength is achieved by:
✔ Oxygen solid-solution strengthening
✔ Cold working during fabrication
Metallurgical characteristics include:
✔ Stable alpha crystal structure
✔ Excellent resistance to stress corrosion cracking
✔ Superior resistance to hydrogen uptake
✔ Maintains passivity in aggressive reducing environments
Corrosion Resistance – Key Advantage
Titanium Grade 7 offers corrosion resistance superior to Grades 1–4 and Grade 9, making it the gold standard for corrosion-critical titanium applications.
Outstanding resistance to:
✔ Chloride-induced crevice corrosion
✔ Reducing acids (sulfuric, hydrochloric)
✔ Sour service (H₂S environments)
✔ Seawater and brine
✔ Mixed acid industrial processes
Grade 7 is often selected where Grade 2 fails due to crevice corrosion or reducing-acid attack.
Fabrication & Processing
✔ Excellent weldability (TIG, MIG, EBW)
✔ Palladium does not degrade weld quality
✔ No post-weld heat treatment required
✔ Very good formability (similar to Grade 2)
✔ Moderate machinability, comparable to CP Grade 2
Advantages of Titanium Grade 7
✔ Best CP titanium for reducing and chloride-rich environments
✔ Excellent weldability and ease of fabrication
✔ Long service life with reduced maintenance
✔ Lightweight with high corrosion resistance
✔ Cost-effective alternative to nickel-based alloys
Limitations
⚠ Higher cost than Grade 2 due to palladium content
⚠ Not intended for high-load structural applications
⚠ Over-engineered for mild environments
Comparison – CP & Pd-Alloyed Titanium Grades
| Grade | Corrosion Resistance | Strength | Typical Use |
|---|---|---|---|
| Grade 2 | Excellent | Medium | General purpose |
| Grade 7 | Outstanding | Medium | Aggressive chemicals |
| Grade 11 | Very High | Medium | Cost-optimized Pd alloy |
| Grade 12 | Very Good | Higher | Industrial balance |
Why Choose Titanium Grade 7?
✔ Operating in reducing acids or chloride environments
✔ Crevice corrosion resistance is critical
✔ Long service life outweighs initial material cost
✔ Weldability and fabrication ease are required
✔ CP titanium grades are insufficient
Titanium Grade 7 combines the fabricability of commercially pure titanium with corrosion performance approaching exotic nickel alloys — at significantly lower weight and long-term operating cost.