You might have had better adhesion by just sanding the covers with a 400-500 grit and spraying a sealer or maybe even just the paint itself.
My guess is that the Dupli-color adhesion promoter does not work unless you are applying it directly to plastic - and not on top of the previously painted surface of these wheel covers. I purchased a can of that product and after further research, never used it. The technical department at Dupli-color did not seem to know if you can use a urethane paint on top of their adhesive promoter. They said if using their adhesion promoter, to use only their brand of paint for the final coat which I wasn't going to do so I just ended up going with a different system.
Fwiw, I had very good luck refinishing some old plastic wheel covers by sanding to remove most of the paint, filling in any large scratches or blemishes with a glazing putty (that is the red product in the first picture), then sealing the covers with an epoxy sealer (i.e. epoxy primer that is thinned down) -
this step is not pictured; and then a final top coat of a single stage silver urethane.
However, one can easily have $80-100 just in material cost as I did. After two years, the paint has not come off except a small area where I ran up against the curb (which would have damage an alloy wheel as well).
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