I have a new model A3 Sportback 2.0 TDI SE first registered end March 2013. Very soon after I bought the car the wheel hubs started to rust. My dealer accepted that this was a problem but said that Audi would not replace the hubs under the warranty. I contacted Audi Customer service regarding the problem. After a lot of communications with them they finally said they considered the problem was only cosmetic and without accepting any liability they would provide hubs free of charge if I would cover the cost of the installation. Finally my dealer, because they said I was good customer, said they would cover the cost of replacing the hubs.
The new hubs have been fitted for about 6 weeks and one is already starting to rust. This seems to be a generic problem and the coating applied to these hubs is not up to the job.