Pitting and corrosion occurring on the rims that came stock on my 2002 vw gti 337. this car was a limited edition vehicle for the usa, with only 1500 made.fitting of rims and black spots are noted, as well as whitish spots that indicate corrosion of the underlying metal. i wash these rims on a weekly basis with a non-acidic wheel shampoo, as well as waxing them on a monthly basis with wheel-specific wax. however, aformentioned condition continues to worsen. *ak