that is odd, as I have my wheels changed for the same reason and the replacement set were finished in a different way which should help avoid the problem again. You will see that the surface finish is different to your original wheel (polished on all surfaces, not partly frosted as original IS wheels).. I must say I do not think the replacements look so attractive.....
However, all I would advise you is to keep the wheels clean as far as possible. The salt in winter attacks them and giving them a wash over regularly, especially in winter to remove the salt. even when not washing the whole car, will help the problem andi well worth it. My second set are fine. I don't know whether your dealer with replace them again.... but at least keeping them clean from salt will definitely help. :winky: