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Loss of Powder Coat Gloss on Sandblasted Parts

I have encountered a 20% loss of gloss on 10 gauge cold rolled steel that has been sandblasted compared to the same part that had not been sandblasted. We have run side by side tests with the same results. I feel this is a result of the flow characteristics of the powder due to the surface profile introduced by sandblasting or an over-bake situation caused from weakening the substrate after the sandblasting.
Has anyone encountered this or have any insight regarding such?

Chuck Stairs
Powder Coat/Paint Supervisor - Rockford, Illinois, USA
2005

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It's easy to determine if you have an over-bake issue, do the same test only under-cure the samples and see if you get the same results.
It's the sandblasting though, 90 grit or finer media should be used to prep for powder, sandblasters automatically load 60 grit unless you specify it because the 60 cost less. Run some samples using 90 or finer and if you still have the gloss problem, it might be a good idea to try different types of media as residue from the blasting embedded in the surface could be contaminating the paint.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2005