Let me move your post over to the 3rd Gen forum so the owners there can answer your question. :thumbsup:

 

A small amount of surface rust there is normal, you would not normally notice it when the stock alloys are installed because the hubs are covered by caps, exposed untreated steel has left the factory and exposed to moisture in the environment and salt so develops a little rust.

 

The first thing I do on my new cars is paint the exposed metal on brake hubs, the edge of the rotors and anything else that is under neath the car that isn't painted than can rust.

 

Rust will form on brake rotors just sitting there in humid conditions or rain. Has done so on every vehicle I've owned and on the aircraft I've worked on. It wears off pretty much immediately upon brake application.