A powder spraycoating apparatus comprising at least one compressed-air outlet (8) connected to a source (14) of compressed air from which it receives compressed air (15) at such a rate and such pressure that the compressed air at the compressed-air outlet (8) shall detach the powder's boundary layer from the powder duct (4) and shall concentrate the powder flow toward the radial flow center and make it swirl, at a site near the downstream end (6) of the powder duct (4).