I'm refinishing a set of Ford's aluminum “bullet hole” wheels. (Thanks, Rick!!!) These came from the factory with a clear coat that protected the polished aluminum, but over time the coating failed and corrosion set in. Most of the damage is where the center cap hits the wheel as well as well as where balance weights have been installed. My guess is that the center caps weren’t always tight against the wheel, allowing them to vibrate and cut into the coating.
It should be noted that this is a hazardous job as it requires the use of chemicals to strip the clear coat, and proper protection such as rubber gloves and safety glasses should be worn. Further, it is a dirty job as it involves sanding aluminum, which creates lots of very fine dust, so a mask would be appropriate.
Here’s what one of my wheels looked like before refinishing: