I've had clear coat on aluminum wheels flake off on prior vehicles, and I assume it was poor surface prep when they were coated originally. You can pursue a warranty claim and see what happens, or pay to have them refinished. Do you use a carwash with one of those automated wheel brushes? Avoiding abrasive brushes and high pressure water spray should reduce it's occurrence. Fortunately I've not had any issues so far with my Expedition wheels.