Grade 2 vs Grade 5 Titanium
The two grades that answer most questions — Gr2 (the corrosion workhorse) and Gr5 (the strength standard). Both get specified for everything; this page draws the line properly.
TL;DR
| Question | Grade 2 | Grade 5 |
|---|---|---|
| Family | commercially pure | Ti-6Al-4V alloy |
| Min tensile | 345 MPa | 895 MPa |
| Corrosion in chlorides | excellent — the benchmark | excellent, same film |
| Weldability | easiest of the two | good, gas discipline |
| Machining | gummy; holds tools honest | standard CNC alloy behaviour |
| Price level | lower/kg | notably higher/kg |
| Best for | seawater, chemical, sheet work | structural parts, bolts, aerospace-adjacent |
Pick Gr2 when corrosion/medium drives the choice, the section is thick enough, and fabrication simplicity counts. Pick Gr5 when strength-to-weight, machined precision parts, or bolt/forging loads drive the choice.
Composition & Properties (published ASTM minima)
| Property | Gr2 (R50400) | Gr5 (R56400) |
|---|---|---|
| Al / V | — | 5.5–6.75 / 3.5–4.5 % |
| Oxygen max | 0.25 % | 0.20 % |
| Tensile min | 345 MPa | 895 MPa |
| Yield min | 275 MPa | 828 MPa |
| Elongation min | 20 % | 10 % |
| Density | 4.51 g/cm³ | 4.43 g/cm³ |
Workability: Forming vs Machining
Gr2 forms and welds with the most tolerance of the common grades; machining is gummy (work-hardens) but forgiving on tool wear. Gr5 machines more predictably for thin sections but demands weld discipline (porosity/contamination) and springbacks differently. Sheet-metal shops default Gr2; CNC shops default Gr5.
Corrosion Behaviour
Gr5's alloying adds modest strength at slight galvanic complexity, but the corrosion reputation belongs to Gr2's CP purity; in oxidising chloride service both perform — in reducing acid, neither is the answer without data (see Gr7). For marine hardware, note the steel-isolation caveat on the marine page.
Price Logic (qualitative, no numbers)
Gr5 carries alloying cost, tougher scrap routing and longer thermal processing. But part-level cost inverts when Gr5's strength lets you machine a smaller section. We quote both grades on the same drawing — often a genuine surprise in favour of Gr2, sometimes the opposite.
Scenario Picks
| Scenario | Pick | Why |
|---|---|---|
| Seawater piping, ambient | Gr2 | corrosion first, no strength need |
| Bicycle frame / tubing | Gr9 | weldability decides |
| Machined bolt / fitting | Gr5 | strength-to-weight |
| Reactor internals, warm chloride | Gr2 (or Gr7 if reducing) | medium data rules |
| Thin loaded bracket | Gr5 | section reduction pays |
| Deep-drawn vessel | Gr1/Gr2 | formability |