My large aluminum boat has tyre stains along the bare aluminum sides of the hull from being tied up to jetties and pens over a long time that use old car and truck tyres as fenders. Being in a pen the wind/wave action can push the hull to rub on the tyres with considerable force. I note in your Q&A the use of heat for paving but would the temperature needed risk buckling the aluminum sides?
305600cookie-checkTyre stains on bare aluminum boat hull
Try oven cleaner. Or if that doesn’t work try Brasso
Maybe, try a spot where it doesn’t matter.