Abstract: In this paper,the behavior of adsorptional substances on the steel cathode has been studied by establishing the curve indicative of the relation between adsorp-desorptive potentials and the differential electric capacities and the polarization curve during copper plating sa well.Results have shown that the prerequisite to improve the adhesive forces of the coatings is to let the initial separating-out potentials of Cu during electric deposition fall within the range of adsorpdesorptive potentials and to possess the active protection on the base-metal surfaces after being eroded and activated.the authors thereby set out an idea so-called"surface active protection"and described the inherent factors influencing the adhesive forces of coatings from the views of the active protection and the metal seperation-out potentials.