The book deals with the phenomena of cathodic and anode heating of conductive materials in aqueous solutions of electrolytes| processes of local boiling up of electrolytes in the vicinity of an electrode with a small surface, the formation of a continuous and stable vapor-gas shell, electrical conductivity in a vapor-gas medium, thermophysical and electrochemical aspects of the anode heating option. A critical review of the results of the use of anodic heating for the purpose of hardening, nitrohardening of medium carbon or tool steels, carburizing and nitrocarburizing of structural steels or iron graphites, oxidation of steel or titanium alloys is given. The phase composition, structure, and performance properties of hardened materials are described. Methods and devices for heating metals and alloys in an electrolyte, processing modes, compositions of electrolytes and the results of their practical use are outlined.For scientists, engineers, as well as teachers, graduate students and students of physical, chemical and technical specialties.