Actually decals are vinyl and range from 2mil to 3.5 pending cast or calender material is used. Powder Coating is 400+ degrees for 10+ minutes depending on powder used ie dupont/3m etc... Yes the decals will move, the adhesive on the back will turn to a slippery mush. Not too mention even if you get it done the powder will not succesfully stick to the sticker causing it to pick and flake. there are methods to get it to stay (certain adhesives) and then it can be done but it will eventually fail sooner than later. I played around with it when I did anodizing, a customer was a powder coater and i did several frames and misc parts.