Blistering when E-coat over nickel plating

A. Microgels, or Impinged microgel inclusions.
I had a big problem with these guys about a year ago. The defect is typically caused by bad concentrate "let downs" or poorly mixed solid adds. Or from a partially dissolved or reacted chemical contaminate added, dragged or transported into the bath. Since it is only happening with your repaired parts It is likely a reaction with something on the surface of your parts. How are you cleaning/activating your nickel before coating? A good start would be to clean or remake your activator and prep/cleansing baths. Try to through a .5-1 micron filter on for a few hours to clean out larger sized particles from your coating bath as well. A combination of all these steps is how I was able to rid our line of them.

Thanks for the response. We do not have issues with any other parts only the nickel sanded. I agree with your comment that there must be a residue of some type on the part that the cleaners are not removing.