PURPOSE: To purify exhaust gas and to improve combustion characteristics of an internal combustion engine, by forming a catalytic layer over the surface of parts such as a piston head, valves, etc. used in the combustion system of the engine and parts such as exhaust ports, etc. used in the exhaust system by way of flame spraying of the powder of a heat-resisting ceramics carrying thereon a catalytic metal.

CONSTITUTION: At first, an undercoating layer 3 of Mo, Ni-Cr, Ni-Al, etc. is applied, by way of flame spraying, over the surface of the base material 1 of parts such as a piston head, valves, a cylinder liner, a cylinder head, a glow plug, etc. used in the combustion system and parts such as exhaust ports, an exhaust manifold, an O2-sensor, an exhaust pipe, a muffler, etc. used in the exhaust system of an internal combustion engine. Then, a layer 2-2 of a catalytic metal is applied over the surface of the powder 2-1 of a heat-resisting ceramices such as Al2O3, ZrO2 or the like that is flame-sprayed over the surface of said undercoating layer 3.