My brakes went at 10,000 miles and I couldnt replace them because I was skint. So ran around on metal for 500 miles before one of my pads finally fell out of the caliper.
Before
During
The entire car was covered in the stuff. most of its gone now, was mid winter at the time so I just removed the iron, or 99% of it and then sealed it back up again. Will be having another go over with iron X and a good clay next month.
not tar. Its like tiny dust particles eaten into the paint, maybe iron as theres a sand casting foundry over the road from where i work, and the **** that comes out the chimenly now n again is bad. Might try this stuff.