I purchased a 57 plate Passat from a VW dealer around a year ago. The vehicle is still in warranty and has 20k on the clock. On a recent visit to the local VW dealer, I was told that a routine check had revealed excessively corroded discs that should be replaced when the brake pads are next changed. I have run cars for 15 years covering high mileage and have never come across this problem, regardless of the fact that they have all been stored on a drive and driven in all weathers. I worry that this is a result of sharp practice by the service department, although even if that is not the case, surely such an issue should not arise with such a relatively new car?