After the mechanical removal with razor blades, pennies, chisels whatever finish off with product such as IRON-X
This removes the remaining iron by chelation, not acid so is safe even on paintwork. The Jaguar 420 in my advert had such grinder marks on the front passenger door - thanks, son. I used IRON-X to remove them then the usual DA and polish of choice.
Acid wheel cleaners are safe on GLASS but not if the runoff goes on the coachwork. I have used the usual Wonder Wheels to remove grinder rash from the shed windows and the tiles in the garage. It would probably be fine for uPVC windows but check a small area first. Wonder Wheels or equivalent is much cheaper than IRON-X.
This removes the remaining iron by chelation, not acid so is safe even on paintwork. The Jaguar 420 in my advert had such grinder marks on the front passenger door - thanks, son. I used IRON-X to remove them then the usual DA and polish of choice.
Acid wheel cleaners are safe on GLASS but not if the runoff goes on the coachwork. I have used the usual Wonder Wheels to remove grinder rash from the shed windows and the tiles in the garage. It would probably be fine for uPVC windows but check a small area first. Wonder Wheels or equivalent is much cheaper than IRON-X.