[jk_olivo]

Hi all,

I have put some copper (60um - electroplated on a gold seed layer of 100nm) in the following solution:   KI + I₂ 
The copper is still there, but is now covered by a thick layer of a "grey compound"...   

I'm really dummy in chemistry... can you help me to find out the formula of that compound ?
How can I remove it without destroy the copper ?

Thanks a lot!

[Borek]

How can I remove it without destroy the copper ?

Chances are you have already etched the copper (perhaps even gold?). Iodine is an oxidizing agent, it could oxidize copper to CuI. But I am just guessing.

[jk_olivo]

I have surely etched the gold (that was my purpose indeed).

The copper is still there, since I have taken a cross-section picture with SEM.
In literature I have found that KI+I₂ does not etch copper but it creates a "compound" over it...

Someone already suggested me CuI... but I am not sure...
Moreover, how to etch it ??  

[Hunter2]

CuI 99%. For sure

[jk_olivo]

Ok, fine

Any idea about how to remove it ??
Somewhere I have read sodium thiosulfate (Na₂S₂O₃)...
But I am absolutely not sure about the source!