Ordered the Surf city spray. I'm a bit worried that there's too much caked on that's been sitting for too long, but I'll update the thread when I try things out.

Would a high pressure washer help too? I can do a few cycles of use at home with a brush, then take them to a car wash to do a few cycles for the really caked on stuff.

 

This stuff gest rid of the black baked on crap on my wife's Volvo. I would bet it would get rid of the iron, but probably your paint too. Sonax would not touch the baked on stuff.

It is an acid wash and you need to dilute it 1:5 parts water. Also use an acid resistant spray bottle. The factory Volvo wheels don't mind this stuff but my son used it on his older Subaru which had some gold paint on the alloy wheels which disappeared.




I would test a bit on the back of the wheel and see how the paint holds up.