Cessation of conventional electrolysis due to the boiling of the electrolyte near the electrode with a smaller surface leads to the formation of a three-or four-phase systems. There are different current flow modes characterized by a set of elementary processes, including chemical and electrochemical reactions, the elements diffusion in the electrode material, deposition and removal of coatings and others. Thermal conditions of plasma electrolytic treatment are associated sometimes with traditional modes of bubble boiling, film boiling and transitional boiling. It is not correct physically in our opinion. The different modes oh the current flow in the electrochemical system must be distinguished in dependence of vapor state near electrode. In this case may be distinguishing a different state of vapor-gas envelope (VGE) that may be continuous or discrete, stable or unstable. Nature of the current flows through envelope would be different. Current flow modes through an electrochemical system are dependent on the voltage. The first critical voltage corresponded to cessation of conventional electrolysis is conditioned by local boiling of the electrolyte in the vicinity of the electrode with a small surface. This voltage (40– 80 V) is determined by the heat evolution value that is sufficient to VGE formation. After the conventional electrolysis the mode of the current interruption take place. This mode is used for surface cleaning on the oxide layers, grease contamination, and coatings. The first critical voltage is found to dependence on the electrode polarity very little. The second critical voltage depended on the electrode polarity relates to possibility of forming of the continuous and stable VGE. Under these conditions the electrode is heated to high temperatures. The temperatures of the anode work pieces may be reached up to 1000°C. The temperatures of the cathode work pieces may be reached to melting point of all metals, if the arc discharge would be take place. The arc beginning is determined by the third critical voltage. Conductivity of the cathode VGE is realized by the stationary electrical discharges such as glow or arc, the current through the anode VGE flows by the emission of electrolyte anions. This mode is used for hardening, annealing, and saturation of the metals and alloys by nitrogen, carbon and boron. The possibilities of the obtaining of aluminum carbide nanocrystals, nanocrystalline structures during the nitriding of stainless steel, nanocrystalline borides of titanium and other promising compounds are shown. The voltages 80–280 V are used at the anodic process and a few smaller at the cathode. Fourth critical voltage relates to anode heating cessation after beginning of the electrical discharges. There is also the version of cathode treatment in a hot or boiling electrolyte, when the VGE is collapsed. In this case a thin surface layer of the sample is heated by pulsed microdischarges with followed fast cooling by electrolyte. Low-carbon steel carbonitriding may be carry out under these conditions. Processes of the plasma electrolytic modifications combined the cleaning and metal-coating of steel surfaces, plasma electrolyte heating of the electrochemical coating and electric spark plating are developed. There is also a method of the longevity increasing of the disk-shaped saws by means of cathode heating, smoothing the surface, doping with boron and carbon and electric spark plating with hard alloys. Nanocomposite layers of tungsten carbide on matrix of titanium carbide were fabricated in electrolyte contained glycerin and sodium carbonate with the addition of WC fine nanopowders. The average size of WC nanoparticles was around 49 nm. The samples were biased to rectangularshape pulsed current produced from a 20 kW power supply. Frequency and duty cycle of the pulsed current were maintained constant at 10 kHz and 40%, respectively during the coating process. The samples microhardness values were reached near to 2580 HV0.5.