Have you used solid parts in 9085 with Cu plating?
How smooth was the surface? Did you do any secondary operations to the surfaces before plating?
My first thought is that it is related to porosity in the AM part.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

I'd agree with Ed. If you didn't do something to seal up the porosity inherent in the AM process, you probably left behind plating solutions in the interstitial pores, and have other areas where bubbles from the part being submerged in plating solution left unplated areas at the surface.

First of all, thanks to you both for your replies. Porosity was what I expected as I have seen things like this happen when beryllium copper was plated with gold without an intermediate plating of something such as nickel. Ed - there was no special operation to smooth or seal the Ultem before the plating. Would you guys say that the copper is diffusing into the Ultem. I did not know that Ultem could corrode. Do you think an intermediate nickel plate would help?
thanks again,
msn.

The ultem is not likely corroding, the copper plating is being attacked by salt-assisted corrosion from the plating solutions that were absorbed into the part, then weeped back out and slowly dried in contact with the copper. Use a sealer of some type on the part prior to plating, preferably a vacuum resin impregnation followed by whatever cure cycle the resin mfgr. suggests.

I am not sure that it would work with 9085, but it is common to solvent wash AM parts to smooth the surfaces and remove any 'lightly adhered' surface material. This is then followed by a post-cure and dry/outgas cycle (sometimes warm with a little vacuum). Maybe you could do this and then incorporate a seal step at the end.
Plating solution trapped under the Cu is also my best guess.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed