Well odd to me. I am at the mo hacking off the rust under my car. Going slow but ok no major problems so far. Occasionally I come across a bit that no amount of wire wheels flap disks or Deox gel will shift. The only way to get rid is to use a chisel and hammer. One blow and its off leaving relatively clean metal under it. Its a very dark blue black and the nearest I can describe it is coal. Same texture, very hard and crumbles if you use pliers. Any ideas what this is? 3 bits so far irregular shape and about 10p size.
Cheers
Robert
Cheers
Robert