What's the black & oily substance on the titanium wire surface?

[Larry-HCENG]

We just received a batch of titanium wires of grade 5 (Ti-6Al-4V). The surfaces are covered by a layer of black & oily substance which can be readily wiped off by a piece of cloth. After wiping, the titanium appears in tan/bronze color. Please see the attached photo. I wonder what the substance is and what kind of surface treatment may result in such appearance? By the way, the titanium wires are imported from EU which are used for bolt fabrication.

 

[metengr]

If you want to positively identify the black/oily substance, send a portion of the wire prior to wiping it to a materials lab and they can identify the constituents. Regarding the surface discoloration, this could be staining related to the substance or from handling. Again, this can be evaluated by a reputable lab.

 

[MintJulep]

Why not start by asking the producer what they put on it after drawing?

Our maybe it's a lubricant from drawing that could be removed simply by adding a suffix to the part number.

 

[btrueblood]

Mint,

Like adding a suffix to make my kids clean up their mess? I usually add the "-or else" option

 

[EdStainless]

What spec was this purchased to, an AMS spec?
If so then this clearly fails to meet the surface condition requirements.
The supplier has some explaining to do.

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P.E. Metallurgy, Plymouth Tube

 

[Larry-HCENG]

It's made to ASTM B348/ ASME SB-348. Yes, we contacted their local branch office here, however, the agent doesn't know what it is.

 

[metengr]

With that, I would send a piece of the discolored wire to an independent materials lab for analysis and tell the agent you plan to share the results.