Process for electrochemically modifying support materials of aluminum or aluminum alloys, which have been grained in a multi-stage process and use of these materials in the manufacture of offset-printing plates

Claim 1

A process for the manufacture of grained support materials of aluminum or an aluminum alloy for use in lithographic printing plates comprising the steps of: (I) mechanically graining the material; (II) treating the material; (III) electrochemically graining the material in an acid-containing electrolyte (IV) treating the material; and (V) anodically oxidizing the material; wherein at least one of the treating steps II and IV comprise cathodic modification of the aluminum support material in a solution of aqueous electrolyte comprising at least one member selected from the group consisting of a water-soluble salt in a concentration from 3 g/l up to the saturation limit and an acid in a concentration from 0.5 to 50 g/l, said cathodic modification comprising the steps of: making the grained support the cathode; adjusting the pH of the aqueous electrolyte to a value ranging from 0 to 11; and applying direct current from 30 to 100 A/dm 2 for from 5 to 90 seconds at a temperature ranging from 15° to 90° C. to remove from 0.1 to 10 g/m 2 of material.