I had to remove a wheel from my Phaeton this week, and replace it with the spare wheel - there was a tiny puncture in the tire, and it was very slowly deflating.
I reviewed the owner manual instructions for changing the wheel, and also the instructions in the Phaeton repair manual. The Phaeton repair manual contains additional information about precautions that must be taken to prevent corrosion from developing on the wheel centering seat (the bevel in the middle of the wheel that makes it easier to fit it on the hub). So, I drove up to my VW dealer and bought a can of the wax spray that is specified for use. It cost about $25.
I have attached some photos below that explain how the spray should be used, and show pictures of a wheel that was installed 3 months ago without using this spray (I had a flat on the same position this summer, and changed it myself in a hotel parking lot).
Instructions from the Phaeton Repair Manual
The wax spray
It comes in an aerosol can.
New wheel before the wax is applied
New wheel after the wax is applied
Wheel showing corrosion if wax is NOT applied
This wheel was in service for 3 months.
Wheel hub showing corrosion if wax is NOT applied
Same position as wheel in photo above - 3 months service.