Hey Andy,
I thought that was you!
Sorry about the WVC! I am working on a new Site, but its taking longer than I expected to retrieve all of my info I had stored before my Host quit on me. I figure I should have a new place up and running in about 3 more weeks.
Anyways, I tried to blow up your pic, but its still a bit fuzzy to see the damage close enough to see whats going on for sure, but lets give it a shot here. Is the damage on top of the surface whereas you can take your finger nail and scratch it, or is it more like pitting into the surface?
If its baked on the surface like someone misted spray paint, or so on, you should be able to get it off with 000 Steel Wool, and follow up with a good Chrome Polish, or Jewelers Rouge, and finish off with a good coat of Wax. The reason for the wax is to try to get a good slick surface to further protect the wheel, and add a slick barrier that should reduce the snow / salt buildup as much as possible.
If the wheel surface is pitted (little nicks into the surface) then their is not much that can be done to repair the existing surface. If this is the case, and it keeps re-occurring, rather than replacing your wheels and having it happen all over again, it may be worth while to look into an alternative like Powder Coating, which is extremely durable, made for harsh environments, and is pretty inexpensive overall compared to wheel replacement. Here in the States, the going rate is around $60.00 per wheel with a five year Guarantee! You can get a whole bunch of colors, or now even several variations of Chrome. Maybe something worth looking into anyways.
Here is the Hyperblack, or (Black Chrome) Powder Coating I am thinking seriously about redoing my wheels in.
Please let me know if this helps, or you need more help on it, and I will see what else we can do.
Take er easy!
Candyman