Hello,  I have noticed that piano plates are coated with a thick
black pigment, sort of like a thick primer, to be able to obtain
a smooth finish on the rough casting.

Is this material still available?  I need some to restore a vintage
AMF pedal tractor, with badly pitted metal.  If I coated the pieces
with this pigment, I can work the finish down smooth, as good as new.
There is nothing that looks worse than painted pitted metal, and
replacement parts for the tractor are not available.

Thanks
Andrew Taylor
Tempola Music Rolls