Pass that detail along to the powdercoater and if it's still a problem sand the coating off unitl it clears.
Or just paint them cylinders and move on. Many times they're not even painted and survive just fine. No one will ever see them any how.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-