I have powder coated step bars on my truck, and treat them the same as the rest of my vehicle.
AIO X 2,
SG X 5, and wash and QD just as I do the rest of the truck.
I have noticed no difference in the finish, and they are holding up as well as the rest of the finish on my truck.
I agree, just treat them to the same TLC as the rest of your finish, and the powder coat should hold up very well. Enjoy!