In this paper, the results of measurements of chemical diffusion of C in weldments of Fe- C-Mn alloys with content of 0-15 % Mn, are reported. Alloys were cast in induction furnace under protective Ar atmosphere. They were hot-forged to rods of diameter 15 mm, machined down to diameter 12 mm, and cut into pieces of 4 mm thickness. These cylindrical samples were metallographically polished. Diffusion couples, welded by electrical impulse, were sealed together with Ti-chips, into evacuated silica ampoules. After that, they were annealed at 1073-1373 K for 96-1.5 hours, respectively. Measurement of C redistribution was done in a normal direction to welding interface using electron-scanning microscope Philips SEM-505WDS equipped with Microspec WDX-2A. Diffusion coefficients of C were obtained and the relations between manganese and carbon were found.