I use them all the time. A tool store by me sells a brand called Face-Off in sizes from 4" up to 7". They're my favorite method for stripping paint and rust. Kind of expensive, but to me they're worth it. I use mostly the 5" size in my Makita GV5000 disc sander. A pack of 5 runs about $20.

They remove the paint and surface rust very fast and leave the surface of the metal ready for primer.

Bob