A fuel gas, usually acetylene or propane, is fed through a central nozzle and
supplies the necessary energy to melt the metal. A second outer annular gas
nozzle feeds a stream of air or an inert gas around the combustion flame,
which accelerates the spray particles towards the substrate and focuses the
Arc spraying is comparable to flame spraying, but in arc spraying a DC
electric arc is used. The arc is struck between two continuous consumable wire
electrodes that form the spray material.