It's not so much rust as corrosion.

While harsh acidic cleaners can do that, I'm sure Oggie is being honest because those who live up north can testify that the salt and chemicals used on icy roads do the same thing.

^^That

Aluminum does corrode.

same problem here
 

I noticed the exact same thing with my rims last spring (08). At first it was merely rust colored water coming from one of my rear centercaps. I took it in and the dealer said everything was fine. This past winter I noticed the pitting you see in the pics on the same wheel. I took it in again and was told it could be replaced under warranty, but I held off because I feared all wheels would soon need replacing. Long story short, all wheels are currently showing the pitting. I took it in this past weekend and am waiting for warranty approval. Like the original poster said, I've always washed the car myself using only mild soad and a sponge. I also spray my car down frequently in the winter to rinse the salt off. I've owned new cars before (at a cost much less than $40 grand!) with never a rust or pitting problem. Hopefully a long term solution is in the works. I would hate to have the same problem a year from now!

All 4 of mine were replaced under warranty on my 2008 G37. I expect after this winter, all 4 will be replaced again on my 2009 G37. I might invest in winter rims this year.

cool, I have the same problem with my rear rims, if they replace the rims will they give me new tires as well?

same thing happened to mine. the dealer replaced three of my wheels for free.

did it come with brand new tires too?

In my case no... the tires are not covered under warranty... YMMV

That damage and the fact that my car has summer tires is why I'll invest in a set of winter wheels and tires. I think you got lucky with your dealer. Some dealers will tell you that's "wear and tear". Road salt eats away the clear coat and then attacks the wheel. It's only a matter of time.

If you check the warranty booklet, wheels are covered, for any reason other than damage from road hazard and the like, for 1 year or 20,000 kms (whatever that is in miles).

If the dealer wouldn't have replaced them I would have fought it. Now, after a year, you are SOL.

For what it's worth I live in Toronto too and my G37xS is 9 months old and the wheels still look perfect. I've never had problems with the road salt damaging the paint / clear coating on my wheels of any car I've owned.

Aluminum doesn't rust, as others said it oxidizes. That looks like the clear coat / paint chipped off and the underlying metal has started to oxidize. Also the plastic center caps have the colouring worn off around the edges which is pretty off. It looks like the center of the wheels was scoured with something.