Weld colour on titanium reads shielding quality directly. Bright silver or light straw indicates good gas coverage; blue, grey or chalky white means the weld picked up oxygen and nitrogen from air and may be embrittled. Titanium is intensely reactive to both above roughly 500 °C, and the oxide thickness sets the interference colour.
Pull a finished titanium weld out from under the torch and its colour gives an immediate warning about shielding quality. A bright silver or light straw bead usually indicates good shielding. A blue, grey or chalky-white weld has picked up oxygen and nitrogen from the air and may be embrittled. Reading heat tint is one of the fastest field checks in titanium welding, especially when aerospace or other critical specifications define colour-based acceptance limits.
Why titanium changes colour at the weld
Titanium is intensely reactive to oxygen and nitrogen above roughly 500 °C. If the molten pool and the cooling weld and heat-affected zone are not fully shielded by inert gas, those elements diffuse into the surface and form an oxide film. The film’s thickness sets the interference colour you see, and the same oxygen pickup that colours it also stiffens and embrittles the metal, the surface version of the alpha case that forms whenever titanium is heated in air.
| Parameter | What the guide states |
|---|---|
| Onset of intense reactivity to oxygen and nitrogen | Above roughly 500 C |
| What sets the colour you see | The thickness of the oxide film formed on the surface |
| Shield until the weld and heat-affected zone cool below | About 300 C |
| Specifications commonly used to define allowable discoloration | AWS D17.1 and AMS 2685 |
The titanium weld colour scale
| Colour | Meaning | Typical acceptance |
|---|---|---|
| Bright silver / shiny | Clean weld, well shielded | Accept |
| Light straw / gold | Very light oxidation | Usually accept |
| Dark straw / bronze | More oxidation | Marginal. Check the spec |
| Blue (light to dark) | Significant oxygen pickup | Often reject |
| Grey | Heavy contamination | Reject |
| White / powdery | Gross contamination, brittle | Reject. Remove |
The progression silver → straw → blue → grey → white generally follows increasing oxygen and nitrogen pickup, and therefore increasing embrittlement risk. Aerospace and critical-weld specifications such as AWS D17.1 and AMS 2685 are commonly used to define allowable titanium weld discoloration. In many acceptance systems, bright silver and light straw are acceptable, while dark blue, grey and white require rejection or engineering review. White tint in particular signals a brittle, oxygen-rich layer that must be removed and reworked according to the project specification.
What the colour does NOT tell you
Tint is a useful first screen, not a full inspection. A weld can be silver on top yet contaminated at the root if the back side wasn’t purged. Colour also doesn’t measure mechanical loss directly. For critical work it is backed up by bend tests, hardness checks and, where required, radiography, but a blue or grey bead is a reliable reason to stop and fix the gas coverage before going further.
| What weld colour does not tell you | What the guide states |
|---|---|
| The condition of the root | A weld can be silver on top yet contaminated at the root if the back side was not purged |
| How much mechanical property was lost | Colour does not measure mechanical loss directly |
| Whether the weld passes on its own | For critical work tint is backed up by bend tests, hardness checks and, where required, radiography |
How to keep titanium welds silver
- Shield generously with argon: torch gas plus a trailing shield to protect the weld and HAZ until they cool below ~300 °C, and a back purge on the root.
- Start clean. Degrease and wire-brush (dedicated stainless brush) the joint; oil, moisture and oxide skin all add contamination.
- Use the right filler. Match the titanium welding wire (ERTi grade) to the base metal and keep it clean and well shielded too.
- Control the atmosphere. Draughts strip shielding gas; chamber or trailing-shield welding gives the most consistent colour.
| Control | What to do |
|---|---|
| Shield generously with argon | Torch gas plus a trailing shield to protect the weld and heat-affected zone until they cool, and a back purge on the root |
| Start clean | Degrease and wire-brush the joint with a dedicated stainless brush; oil, moisture and oxide skin all add contamination |
| Use the right filler | Match the ERTi grade of titanium welding wire to the base metal and keep it clean and well shielded too |
| Control the atmosphere | Draughts strip shielding gas; chamber or trailing-shield welding gives the most consistent colour |
FAQ
Is a straw-coloured titanium weld acceptable?
Light straw is usually accepted; dark straw is marginal and should be checked against your specification. Blue, grey and white are normally rejected.
What does a white titanium weld mean?
Gross oxygen/nitrogen contamination, a brittle, oxide-rich surface. It is rejected and must be removed; improve shielding and re-weld.
Can I just polish off the colour?
Removing the tint cleans the look but not the embrittlement underneath if pickup was heavy. Light tint can be cleaned; blue/grey/white indicates the weld itself is suspect, not just the surface.
Why does oxygen embrittle titanium so easily?
Oxygen is an interstitial that strengthens but sharply reduces ductility. See interstitial elements in titanium. A contaminated weld has locally high oxygen, hence the brittleness.
Writing the colour requirement into the order
Colour is judged at receiving, but it is decided at ordering. Where the purchase document says nothing about shielding coverage, acceptance basis or what happens to a rejected length, the fabricator fills each gap with a house default, and the argument at incoming inspection is then about whose default applied rather than about the metal.
| Line on the order | What it settles | What happens if it is left blank |
|---|---|---|
| Acceptance basis for weld appearance | Which written scale or drawing note a colour is judged against | Two parties compare the same weld to two different references |
| Inspection coverage | Whether every weld is examined or a sample is | A sample result is read as a lot result |
| Reports required | Which records arrive with the goods beyond those the specification already mandates | A fully compliant certificate answers less than incoming inspection expects |
| Marking | What is stamped or tagged on the piece, and what is not | Label wording and certificate wording drift apart |
| Disposition of rejected material | What happens to a rejected length before the question becomes a dispute | The commercial decision is taken after the fact, under time pressure |
Three of those five lines already appear as expected order items in the bar and billet specification ASTM B348, namely marking, the reports required and the disposition of rejected material (ASTM B348, ordering information). That specification governs bar and billet rather than welded fabrication, so it does not settle a weld order. It does show that even a plain mill product is not considered fully ordered until those three lines are answered, and a welded assembly needs them no less.
Specification detail with sources
ASTM B265 sets the interstitial window that weld colour is ultimately guarding: Grade 2 base metal is limited to 0.25 percent oxygen, 0.03 percent nitrogen and 0.015 percent hydrogen by weight, and a weld that has run blue or grey has locally overrun allowances that tight. The same chemistry logic is why AWS D17.1 and AMS 2685, the two acceptance documents this page names, judge titanium welds on colour rather than on bead profile, since the pickup happens wherever the metal sits above roughly 500 degrees C without full argon coverage.
Beiyu Titanium supplies its titanium filler wire cold drawn with a bright or acid-pickled surface, so no oxide skin rides into the pool on the wire itself, in straight lengths from 0.8 to 6.0 mm diameter up to 6000 mm long. The EN 10204 3.1 mill test certificate supplied with the order reports the heat chemistry including oxygen, nitrogen and hydrogen, and in Beiyu’s 15 years of titanium export work those three gas lines are the certificate fields a fabricator reads first when a tinted weld puts the filler under review.
Send a technical RFQ
For titanium welding wire RFQs, include AWS A5.16 / ERTi grade, diameter, spool or straight-rod form, quantity, shielding requirement and any weld-color acceptance criteria.