| 摘要 |
PURPOSE:To obtain an aluminum base for a printing plate provided with a grain in which the pits having a large depth as compared with the diameter thereof are present uniformly and densely, without generating any transverse streak form treatment marks, by using a specified AC current in a method of electrochemically graining an aluminum base by using an AC current in an acidic electrolytic liquid comprising nitric acid. CONSTITUTION:An AC current with a frequency of 60-140Hz and a ratio tF/T of anode time tF to period T of 0.33-0.15 is used as an electrolyzing power supply waveform, in a method of electrochemically graining an aluminum base by using an AC current in an acidic electrolytic liquid comprising nitric acid. The aluminum base may be, for example, a pure aluminum plate or an aluminum plate containing at least 0.3% of Mn. The AC current waveform is most preferably a rectangular waveform. A preferable example of the electrolytic liquid is an aqueous solution containing 5-25g/l of nitric acid, the temperature thereof being preferably 20-60 deg.C. The average current density is preferably 10-50A/dm<2>. The duration of the electrolytic treatment is preferably 10-120s.
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