Removing black scale after forging

Wire brushes are your friend. You can buy hand brushes, and you can buy knotted cup wheels that thread onto the spindle of a 4 or 4½" angle grinder. Those are one approach. Another approach is tumbling parts in abrasive media, or, equivalently, vibrating the parts in abrasive media. This can be fast and very effective but it's costly to set up and expensive, more of a production thing. Finally, you can do various chemical etches, varying anywhere from muriatic acid to molasses. The black is an iron oxide, and the basic concept is that acids attack oxides much more strongly than they do base metal. Acid dips have some drawbacks.

Google tells all.

GWE

Plain vinegar works great. Dip or brush it on and the scale will fall off in minutes.

Hand wire brush the piece quickly when you remove it from the forge. If you don't, the scale will be driven into the surface from your hammering, making it rough.

Scale will come off at a lower heat than it forms at, so a final brushing (at red heat) before letting it cool is also pretty effective.

Steve

John wrote:

A few licks with a butcher block brush each time the piece comes out of the fire will make final clean up much easier.

You can get a butcher block brush at most farrier suppliers.