Process for anodizing aluminum foil
AssigneeSprague Electric Company
InventorsJohn A. Ball, John W. Scott
Life of this patent
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Abstract
In an integrated process for the anodization of aluminum foil for electrolytic capacitors including the formation of a hydrous oxide layer on the foil prior to anodization and stabilization of the foil in alkaline borax baths during anodization, the foil is electrochemically anodized in an aqueous solution of boric acid and 2 to 50 ppm phosphate having a pH of 4.0 to 6.0. The anodization is interrupted for stabilization by passing the foil through a bath containing the borax solution having a pH of 8.5 to 9.5 and a temperature above 80.degree. C. and then reanodizing the foil. The process is useful in anodizing foil to a voltage of up to 760 V.
Claims8
In an improved process for the anodization of aluminum foil for electrolytic capacitors including first forming a hydrous oxide layer on said foil prior to anodization of said foil, and repeatedly interrupting said anodization to stabilize said foil in a mildly alkaline bath, the improvement comprising conducting said anodization in a bath containing an aqueous solution of 10 to 120 g/l boric acid and 2 to 50 ppm phosphate as electrolyte at a pH of 4.0 to 6.0 and a temperature of 85.degree. to 95.degree. C., whereby said foil can be anodized to 760 V without scintillation.
Dependencies are inferred from the claim text.