Q: We are observing significant fading on orange powder-coated parts. Is this what could happen if powder is not cured all the way?
A: That can happen from undercure of nearly any chemistry and/or the use of the wrong powder chemistry (e.g., hybrid instead of polyester). I would check with your powder coater and verify what product they used and if they have records from their oven operation.
I would also perform a solvent rub test on the affected part(s). If the coating is easily removed with less than 50 double rubs of a cloth soaked in acetone, the coating is undercured.