| 摘要 |
PROBLEM TO BE SOLVED: To increase capacitance by subjecting an aluminum foil to a final annealing step after subjecting the aluminum foil obtained by hot rolling and cold rolling to an electrolytic etching step at least once to thereby form a nucleus for forming an etched pit. SOLUTION: When an electrolytic etching step, i.e., an AC etching step in an aqueous solution containing a chloride is performed at least once before a final annealing step after an aluminum slab has been soaked, hot-rolled and cold-rolled into an aluminum foil, a porous etched layer wherein a great number of fine cubic etched cells are arranged in lines is formed. Part of this etched layer is destroyed and aluminum is thus dissolved out. By taking advantage of the fine asperities containing film defects of cells formed by the dissolved aluminum, an etched pit can be formed uniformly at a high density by DC electrolytic etching performed after the final annealing step. Recesses formed by preventing the uniform growth of an oxide film in the final annealing step are utilized as a nucleus for forming the etched pit. The aluminum foil wherein the nucleus for forming the etched pit is uniform at a high density can improve face enlargement ratio and increase capacitance.
|
