They appear corroded, but only AROUND the center caps....caps themselves are fine, most of the wheel surfaces are fine, looks like something was inside/under the center caps and got spun out onto the wheels as the RPMs created centrifugal force.
Using fine grit sandpaper I can remove it, and there is only minor pitting on one of the wheels. So sand it off, polish, and clear coating seems to be the answer.

Any ideas on how this happened? what solvent/acidic/corrosive stuff might have put in there to cause this? It is black, so whatever turns aluminum black?

Also, any product advice to make these wheels look new again?

I am thinking a little effort on my part can save them.

 

Meguiars has a great chrome wheel cleaner and Mothers has the 'power ball'.
FF

 

i hear ya, it makes your wheels look like crap!

 

aluminum oxidizes black that would be my first guess but sounds like the steps you mention will be the best way to correct this

 

Are the center caps a different metal than the wheel? It can be causing a reaction with wet salty parts.
FF

 

very true in places it snows alot the way they salt the roads can cause that and i know that some bearing grease is black if some of that washed out through the seam of the center caps and wheels when it dries it can be abrasive and cause the pitting to.

 

I had a set of chrome plated wheels on my 2007 Durango that after fours years were pitting so bad inside and outside the wheel that the tires were losing air constantly. I had to buy the OE chrome clad wheels again as I sold them four years ago. Chrome wheels and salt do not mix well in Pittsburgh. Does Utah get a lot of snow?
FF

 

i have a buddy with a lifted excurtion and his dad owns a chrome shop so they chromed his whole suspention and he we to galveston tx for off shore work and all the salt there rusted every bit of it. I dont think i could make it in pittsburgh with all that salt lol

 

Certain brake dust also has an etching effect.