powder is more durable then paint I would not worry too much unless you are using an acid wheel cleaner.
Came home one day to find that my girlfriend was washing her car. She discovered the wheel cleaner I have for my truck and used it on her cavaliers painted hubcaps and then was confused as to why there was no paint left on them 5 mins later.....
Almost any powder coater will tell you to wash the PC'd item with only a mild soap and water. ANY chemical based wheel cleaner will ruin the finish on powder coat. I had the wheels done on my Speed3 twice. First time, the shop that did it said that it would be fine to use a cleaner for them. Sure enough, after the first wash, it created streaks through the finish that almost looked like runs in paint.
The second shop i took them to specifically said to NOT use any wheel cleaner to clean them. A mild soap and water is all that is needed/recommended to clean powder coated stuff. Also, do not use a scrub brush unless it is very soft. Like mentioned above, powder coat is pretty resistant to stuff sticking to it so water and soap is great at cleaning it.
