Corrosion resistance, weldability and formability first: GR2. Strength and stiffness first: GR5. Minimum tensile strength is 345 MPa for GR2 and 895 MPa for GR5. Corrosion resistance is similar, so a corrosion-free structural part is usually GR5 and a corrosion-free equipment part is usually GR2.
TITANIUM · GR2
GR2 commercially pure titanium parts — corrosion-resistant titanium for seawater, chemical and electrolyser service
GR2 is the most widely used of the four commercially pure titanium grades, balancing strength and formability; it does not corrode in seawater, chloride or oxidising acid service and welds easily. Octud supplies GR2 CNC-machined parts and welded structures from customer drawings.
Where titanium is chosen because it does not corrode, the grade is usually GR2. Load-bearing parts go to GR5, but in seawater, chloride, electrolysers and chemical plant the corrosion resistance and weldability of CP titanium come first.
Commercially pure titanium is graded by oxygen content from GR1 (softest) to GR4 (strongest). GR2 sits in the middle with tensile strength of at least 345 MPa and elongation of at least 20%, is available as plate, tube and bar, and welds easily — which made it the default grade for process equipment. Corrosion resistance comes from the surface oxide film and differs little between grades; reducing acids (hydrochloric, concentrated sulphuric) call for the palladium-bearing GR7 or GR16.
Machining behaves opposite to GR5: soft and gummy, chips weld to the edge and the tool pushes. Sharp tools and adequate feed are needed, and thin walls deflect under cutting force. Conditions cannot be copied from GR5.
The growth area for GR2 enquiries in Korea is water electrolysis. Porous transport layers (PTL), bipolar plates, end plates and fittings in PEM stacks see acidic, high-potential service where titanium is the standard, mostly in CP grades. Seawater heat exchangers, desalination fittings and flanges, and chemical reactors follow the same logic.
Specification requirements — ASTM B348 GR2 (bar)
- Chemical composition
- Fe ≤0.30 · O ≤0.25 · N ≤0.03 · C ≤0.08 · H ≤0.015 (wt.%) · balance Ti
- Tensile strength
- 345 MPa min.
- Yield strength
- 275–450 MPa
- Elongation
- 20% min.
- Density
- about 4.51 g/cm³
- Standards
- ASTM B348 (bar) · B265 (plate) · B338 (tube) · F67 (medical CP titanium)
- Welding
- Easy — TIG · plasma, shielding essential
ASTM B348 · B265 · F67
Where it fits
- PEM electrolyser stacks — PTL · bipolar plates · end plates
- Seawater heat exchangers · desalination
- Chemical reactors · strainers · piping fittings
- Flanges · fasteners · tubes
- Medical devices — ASTM F67 CP titanium
- Welded tanks · housings
Before ordering
- 01Contact medium and temperature — reducing acids call for GR7 or GR12, not GR2
- 02If strength drives the design, go to GR5 — GR2 is about corrosion, forming and welding
- 03For welded structures, specify weld inspection scope (visual, penetrant, radiographic) on the drawing
- 042D (PDF) + 3D (STEP) together
Quotation and samples run through the Titanium parts page — the form is at the top of it.
Send a drawing for a quote