You have to ensure the time/temp cycle is kept low and short enough otherwise you will affect the heat-treatment of the forgings. You can powdercoat, if you're careful. We do it everyday. We switched all of our standard colors to powdercoat once they developed metallic powdercoats and got the cure temps down to an acceptable level, so these days it is possible if done properly. We find powdercoat to be more robust, but you get more color options with paint so we still have to use paint for color matched wheels unless we've had a custom color developed in volume (Arctic Silver for example).