Same thing here, Paul. Tire was carroded to the wheel rim. Got the bike from back east, from I believe it was Pennsylvania if memory serves. Had it shipped to me. Nice machine. Ran like a champ. But it came with two broken rear spokes, something I knew when I bought it.
The day came when I figured I'd better fix that situation. That's when I discovered how corrosive the weather back east can be on things like where tire beads seat themselves against the inside of a wheel rim.
Don't remember much in the way of alloy dust, just gummy crumbly dark gunk that acted as a kind of super cement between the wheel and the tire. Never saw anything quite like it before, and hope to never see it again..
"Never let your sense of morals get in the way of doing what's right." Isaac Asimov's 100th birthday 01/02/2020