I know this has been discussed many times before, I also appreciate brake discs are largely exposed metal, the obvious reasons for why this has to be and their vulnerability as a result.   Saying that, it's 2018 and the rear discs on VAG (and other manufacturers) vehicles continue to develop significant corrosion on the easily visible non-contact surfaces.   How hard can it be to paint or sufficiently protect them? No doubt it's more expensive, sure I can paint them myself, b