I read your July 2003 column referring to adhesion problems on zinc-plated parts. I had a similar problem, which was traced back to the plating failing during baking. The reader should chat with his zinc-plater to see if his plating will withstand the powder coating cure baking temperature. C. J.
You are right that the zinc plating can fail under some temperature conditions experienced during the cure of the powder coating. However, when this happens you normally see the plating metal, or metal chips, on the back of the powder coating that flaked-off the part. This person saw black specs on the back of the powder coating chip. I think he has a different problem from yours.