⚡ Key takeaways
- Titanium is expensive lightness: 40 % lighter than steel at comparable strength. Ti-6Al-4V has a density of 4.43 g/cm³ and 900–1,100 MPa tensile, one of the highest specific strengths of any structural material.
- Commercially pure titanium (Gr1/Gr2) belongs in medicine. Biocompatible, non-sensitising and non-magnetic, it is used for bone screws, dental implants and surgical instruments.
- Ti-6Al-4V (Gr5) is the aerospace workhorse: airframes, eVTOL, motorsport and high-end sports equipment.
- Titanium's trump card is corrosion resistance. Seawater, chlorine and acids barely touch it — roughly ten times the resistance of stainless.
- But titanium galls. Two titanium threads driven together seize; lubricate, or coat with MoS₂.
- Watch galvanic corrosion. Titanium sits at about +0.02 V, so in contact with aluminium or steel it accelerates attack on the other metal. Isolate the interface.
- Cost is ten to twenty times steel. Use it only where weight, corrosion or medical requirements are genuine.
Contents
2. Core properties
3. Three applications: medical, aerospace, corrosion
4. The critical weakness: galling
5. Galvanic corrosion
6. Decision tree
1. The titanium family
| Grade | Type | Tensile (MPa) | Use |
|---|---|---|---|
| Gr1 / Gr2 | Commercially pure | 240–340 | Medical, chemical, thin-wall |
| Gr5 (Ti-6Al-4V) | Alpha-beta | 900–1,100 | Aerospace, eVTOL, premium parts |
| Gr23 (Ti-6Al-4V ELI) | Extra-low interstitial | 800–900 | Implants, high toughness |
| Gr7 (Ti-0.2Pd) | Corrosion resistant | 400 | Chemical plant, chlorine |
2. Core properties
- Density 4.43 g/cm³, 56 % that of steel.
- Highest specific strength of the common metals.
- Service range -200 to +600 °C.
- Non-magnetic.
- Biocompatible.
3. Three applications
3.1 Medical
Bone screws, dental implants and stents use Gr2 or Gr23: no sensitisation, no rejection, no magnetic interference with imaging.
3.2 Aerospace and eVTOL
Airframe fasteners in Gr5, where saved mass converts directly into range.
3.3 Marine and chemical
Desalination plant and offshore platforms use Gr7 for chloride resistance.
4. The critical weakness: galling
Titanium conducts heat poorly and is highly adhesive. Two titanium threads driven together:
- Friction raises the surface temperature.
- Material transfers and welds.
- The joint seizes halfway and cannot be taken apart.
5. Galvanic corrosion
Titanium is noble at about +0.02 V. Against aluminium (-0.8 V) or steel (-0.6 V):
- The aluminium or steel becomes the anode and corrodes.
- The titanium is unaffected.
- An insulating sleeve or washer is mandatory.
6. Decision tree
- Implant? Gr23 ELI.
- Aerospace weight saving? Gr5 Ti-6Al-4V.
- Seawater or chemical? Gr7.
- Titanium on titanium? Add lubricant or change to a steel bolt.
- Budget sensitive? Use aluminium or stainless instead.
FAQ
Q. How is titanium graded? Not by 8.8/10.9 but by alloy: TA2 for commercially pure, TC4 for Ti-6Al-4V at about 900 MPa.
Q. Does titanium gall? Yes, worse than stainless. Use low speed plus lubrication or a coating.
Q. How much more does it cost? Five to ten times steel for finished parts, but it saves 40 % of mass — worthwhile in aerospace and medical work.
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