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Surely paint or a sealant on the surface would stop it?
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Ford "Pepperpots" iirc, and a few others, I think the wheels made by GKN, and were as porous as a sponge!
They would corrode around the bead seating area. Out of everything we tried, blasting and powdercoat seemed to work best... for a few months! until the bead of the tyre wore its way through the powdercoat, and it was back to square one! wheels these days seem to be far better quality, and rarely do you now see flaking lacquer like you used to 10 years ago
Probably they had to up the game because of warranty claims!
Thom