Carbon arcs are typically 35v - 90v, and use high current not high voltage. The vacuum would be a few mm of Hg, not as high as a radio tube. The vapor deposits on pretty much anything cooler than it, you have to shield what you don't want coated. Electron beams have been used to heat the coating materials, remember Fuji EBC coatings?
Originally Posted by Tom1956
The trouble is that anything in a vapor phase will deposit on anything cooler than it, so I don't think a carbon arc would produce a clean enough MgFl vapor to result in a useful coating. It would sure supply the heat though.
Look into the work done by Katherine Blodgett for Generous Electric.