Solving "Grey Compound" Mystery: Copper + (KI + I2) = ?

[jk_olivo]

Copper + (KI + I2) = ?

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"... Huh

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!

 

[chemisttree]

What was underneath the gold and how do you know the copper layer is still there?