How much salt do they use to melt the winter roads in Idaho?

My guess: you're seeing pitting in the aluminum alloy wheel with added effect from the chrome plating. Best thing would be to keep your wheels and undercarriage rinsed if any salt film begins to show. The next thing to do is contact your IDOT maintenance shop and ask them if they're using salt deicers.

Common chloride salts are cheap and effective, but they have all kind of nasty effects on water quality and the environment, not to mention metals. There are better alternatives like calcium magnesium acetate (CMA) and potassium acetate (PKA) that have little if any adverse effects on anythign and can be absorbed by plants.

So, you might want to impress-upon IDOT to change deicers.

Of course, if you've not been driving in winter road conditions, it may just be naturally occurring salts. Again, keep you're rims clean. I don't know much about waxes n' wheels, but a good coat of wax might also keep the elements off of your wheels.

About your door-dinged cladding, I can only say don't try to get close-in parking spaces. I park in the outer rim of the galaxy to minimize encounters with careless drivers, hostile consumers and -worse -shopping carts when I'm parked in a lot.