PVD adhesion to polyester powder coat

I run a shop that specializes in powder coat on composites and non-conductive substrates. We use a proprietary pre-coat solution that temporarily allows surfaces to become conductive so they can be powder coated. I can get the powder on whatever substrate but I am having a hard time getting a PVD layer to adhere to the cured powder. Generally PVD over powder is done with high film build, high flow epoxy, then plasma treated, PDV, and a final top coat.

I want to find a chemical adhesion promoter (or surface etching) that will provide adhesion to a polyester base coat without a plasma treatment. In trials, we can get the metalized layer onto the part, it just flakes right off.