The invention relates to a method for grafting an organic film onto an electically conductive or semiconductive surface by electro-reduction of a solution, wherein the solution comprises one diazonium salt and one monomer bearing at least one chain polymerizable functional group. During the electrolyzing process, at least one protocole consisting of an electrical polarization of the surface by applying a variable potential over at least a range of values which are more cathodic that the reduction or peak potential of all diazonium salts in said solution is applied. The invention also relates to an electrically conducting or semiconducting surface obtained by implementing this method. The invention further relates to electrolytic compositions.