Been working on my wheels trying everything in the garage. Finally broke out the little bottle of wheel and tire cleaner from HD and used a pad similar to scotchbrite and it was the answer. The stains came off fairly easy. Good Luck

 

S100 or any cleaning that is comparable left on and dried will leave a stain like that and it can be heck to get off. I detail bikes for extra income and use mothers wheel cleaner. There are 3 types, 1 liquid and 2 paste. I use the paste most of the time. 1 is like 4.98 and the other is 14.98. The 14.98 is called billet and I use it to finish with. It will remove almost anything. The good part is when you clean with the aluminum paste (your choice) it treats the wheel so it is easier to clean the next time and doesn't stain as easily. It protects the wheel. There is also sealers that can be used to make the finish last even longer. I do not use sealers. When I work the wheel with the paste it lasts up to 6 months unless I get something on it that does stick. Break dust doesn't stick very good if done correctly.
I will not use never-dull or steel wool on aluminum they will leave scratches. The never-dull is good on hard chrome like wheels to remove rust but not show chrome like breathers, pipes, dashes, lights etc...
So far I have had no complaints with my work and I have been doing it a long time.
This is my thoughts nothing more
dd

 

Have you been riding on a road where deicing chemicals have been recently used? That looks like magnesium chloride corrosion to me. The wheels I've seen at the dealer's look like they're clearcoated. Maybe yours didn't get coated at the factory.

 

The wheels are not clear coated
it is simple to find if something has a clear coat on it. Use what ever, like mothers, and if it doesn't turn dark (most likely it will be black) there is a coating of some type on it.

 

yes it sure does look like salt or liquid salt that has been on the roads

 

glad I got rid of my 09 rims and put on chrome screaming eagle rims. my 2003 aluminum rims drove me crazy. I used mothers aluminum polish along with a polishing cloth wheel on a hand drill. you wont believe how black the polish gets as it removes oxidized aluminum. cleaning the polish spatter off the tires sucks but these rims are not coated so they corrode pretty easily. Pez has a good point of figuring out what did this ,cause it will probably keep doing it. not sure if you would want to pull the rims off and have them chromed-if you havent seen any already done in here they look unreal. probably some posts in here still floating around