Abstract: An aluminum plate is subjected to electrochemical surface-roughening treatment etching treatment, and an additional electrochemical surface-roughening treatment in an acidic electrolyte, in the stated order. The electrochemical surface-roughening treatment is carried out in an electrolyte containing nitric acid by using alternating current. The resulting plate has excellent printing performance and long running characteristics.

Abstract: A process for producing support for aluminum printing-plate in which an aluminum support is electrochemically surface-roughed uses an alternating current in an acid electrolyte containing nitric acid. The alternating current has a waveform in which the frequency is within a range of 60 to 140 Hz and the ratio of an anode time t.sub.F to a period T, that is, t.sub.F /T, is within a range of 0.33 to 0.15, and this current is used as an electrolytic power source.

Abstract: A method of continuously electrolytically treating a metal web in an electrolytic liquid using an alternating waveform current via a pair of main electrodes such that the surface of the metal web experiences both an anode reaction and a cathode reaction. The ratio of the current value contributing to the anode reaction acting on the surface of the metal web and the current value of the cathode reaction acting on the surface of the metal web is controlled by shunting a portion of the supplied current to an auxiliary electrode, which is separated from the main electrodes, as a direct current.

Abstract: A process for producing an aluminum support for a printing plate, which involves electrochemical graining of the support, is disclosed. The support is passed through an acidic electrolyte of an electrolytic cell along a path of travel maintained a distance above alternatingly distributed anodes and cathodes in a face-to-face relationship with the aluminum-containing support. Simultaneously, there is applied a d-c voltage between the alternating anodes and cathodes to produce an electrochemically roughened support.The electrochemically roughened supports produced in accordance with the invention have a grained structure. characterized by a uniform and dense distribution of high depth-to-diameter ratio pits and exhibit satisfactory print quality and running characteristic without causing any uneveness.