NOVELTY - Forming a carbon film on a metal substrate at a low temperature, involves preparing a metal substrate having a softening temperature; forming a catalytic layer having a thickness of greater than 0.01 mu m on substrate; and forming a carbon film on catalytic layer by chemical vapor deposition (CVD) at a temperature lower than the softening temperature of substrate, where a carbonaceous material is carried into a CVD reaction area by a carrier gas and is thermally decomposed at 300-1000 degrees C to form the carbon film having a thickness of 1-10 mu m on catalytic layer.    USE - For forming a carbon film on metal substrate in the manufacturing bipolar plate of fuel cell, and also used to e.g. manufacturing carbon nanotube powders, carbon nanotube display boards or carbon nanotube light emitting devices.    ADVANTAGE - The method forms carbon film having high conductivity, being anticorrosive and bonding well to the metal substrate. The method improves anticorrosiveness of the metal substrate. The carbon film has better anticorrosiveness than protective films such as titanium nitride (TiN), metal carbides and metal oxides. So forming the carbon film on the metal substrate keeps the metal substrate from being corroded by the hostile fuel cell environment. The method increases conductivity of the carbon film. The method reduces the reaction temperature of the CVD. The method forms a catalytic layer on the metal substrate to reduce the reaction temperature to less than 1000 degrees C and facilitates carrying out CVD on a metal substrate having a low softening temperature. The carbon film formed by the method is produced at a temperature less than 1000 degrees C, so the carbon film is continuous and fine, and isolates the metal substrate from the hostile fuel cell environment.    DETAILED DESCRIPTION - Forming a carbon film on a metal substrate at a low temperature, involves preparing a metal substrate having a softening temperature; forming a catalytic layer having a thickness greater than 0.01 mu m on the metal substrate; and forming a carbon film on the catalytic layer by chemical vapor deposition (CVD) at a reaction temperature lower than the softening temperature of the metal substrate, where a carbonaceous material is carried into a CVD reaction area by a carrier gas and is thermally decomposed at a reaction temperature of 300-1000 degrees C to form the carbon film having a thickness of 1-10 mu m on the catalytic layer. The CVD is thermally decomposed chemical vapor deposition, plasma enhanced chemical vapor deposition (PECVD) or microwave chemical vapor deposition. The catalytic layer is formed by evaporation, sputtering, electroplating or electroless plating. The method further involves reducing the catalytic layer with hydrogen, before the step of forming a carbon film on the catalytic layer. The operating gas pressure in the CVD reaction area is 0.001-760 torr. The reaction temperature is 800-1000 degrees C.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of the method for forming the carbon film in a metal substrate at a low temperature.