Results are given of theoretical and experimental investigations of the physical characteristics of a free electric arc moving in a self-magnetic field along metal surfaces of different shapes contaminated by dielectric deposits. Similarly to welding, a direct-action arc is used, when the material being cleaned is one of the electrodes stabilizing the electric arc. Compared to plasmotrons, a facility using rail-gun arcs may exhibit a higher specific heat flux. This enables one to attain higher efficiency and capacity by reducing the loss of heat for heating the plate to be cleaned. Experiments are performed with steel samples contaminated by paraffin films. Data are obtained on the rate of arc propagation and its geometric characteristics, on the heat flux to the electrode being cleaned, on the cleaning capacity at different amplitudes of current, and on the thickness of paraffin coating. The basic possibility of removing dielectric deposits from metal surfaces with the aid of electric-arc treatment is demonstrated.