I think you may find that after you get these off & close inspection, that you may have some actual corrosion coming up from the aluminum surfaces under the paint, possibly because the area was not properly prepped before.
My machine was badly corroded from years of exposure in storage in salty ocean air.....
My solution was to get a big round water heater spill tray & plug the drain hole.....using that for a scrub pan.....a couple of small 2X4 pieces around the edge to support the wheel rim on center. I wasn't worried about the tyres, cause I planned on replacing them anyway.
I used a combination of chemicals, including phosphoric acid and or industrial strength commercial "Purple Cleaner" along with a couple dozen "wire toothbrushes" from the home improvement center and a couple of boxes of latex gloves. Followed by doses of clear water from a spray bottle for rinsing.
After scrubbing all the old finish + all the black corrosion out of all the tiny pits & corners, I refinished the wheels with "dupli-color" wheel paint + 2 layers of clear from the local auto parts store.
If I were doing it again, I would probably powder coat them next time.
As I remember, it took me about a week for each wheel. As I said, mine were really nasty.
Before:
After:
Regards, Ibj...