PURPOSE: To uniformly coat zinc on the surface of a perforated aluminum pipe with good productivity in a simple installation and process by blowing zinc powder on the surface of the perforated aluminum pipe just after extrusion, melting and diffusing zinc with the remaining heat of the above-mentioned pipe.

CONSTITUTION: Metallic powder of zinc is blown on the surface of a perforated aluminum pipe 2 just after extrusion through nozzles 3, 3a. In this case, the positions of the nozzles 3, 3a apart from the outlet of an extruder 1 are set by moving and regulating them to such distance that the surface to be blown of the pipe 2 is made to the proper temp. and also the amount of zinc powder supplied to the nozzles 3, 3a is controlled according to the extrusion velocity of the pipe 2. The surface of the pipe wherein an oxidative film is not formed just after extrusion and it is in a state enriched with activity can be regulated to uniform and good layer coated with prescribed thickness of zinc because zinc powder is melted and diffused with the remaining heat of the pipe 2.