The present paper contains the results of some theoretical and experimental investigations on phenomena that take place at the interaction of electrical discharges in impulse with the surfaces of electrodes. Based on these results the author demonstrates the possibility of applying electrical discharges in impulse at modifying the microgeometry of piece surfaces, their cementing and microoxidation depending on the imposed conditions of functioning. An ample influence of different factors on the intensity of electroerosion process is analyzed in this work. The functional dependences of the electric as well as non-electric factors are established. The intensity of the process is an exponential function depending on the heat accumulation coefficient. The impulse duration is also influences the electroerosion character. It is underlined that short electric discharges are "anodic" and those of long duration are "cathodic". Additional application on the gap of electric or magnetic field provokes amplification of electrodes' erosion and stratum formation. The analyses of the results of experimental investigations on physico-chemical effects which are produced in the piece surfaces processed by applying electrical discharges in impulse (EDI) are made. It is stated that EDI cause micro-metallurgical phenomena, diffusion effects, chemical and structural modification of the machined surface composition and of its microgeometry. The graphite film formation provokes partial surface hardening simultaneously serving as ointment in solid state, the result being the increase of machined piece functional performances. All this contributes to increasing the hardness of the active surface and the absorption properties of different types of radiation.