Sprague Electric Company

John J Randall, Jr

Walter J Bernard

Mulk A Arora

Aluminum electrolytic capacitor foil is etched in a bath containing 0.7 to 2.O M hydrochloric acid, 0.2 to 0.5 M hydrated aluminum trichloride, and 0.02 to 0.4 M phosphate ion while subjected to the action of alternating current at 35 to 55.degree. C.

AC Etching of aluminum capacitor

Aluminum electrolytic capacitor foil is etched in a bath containing 1.0 to 1.8 M hydrochloric acid, 0.25 to 0.5 M aluminum chloride, 0.2 to 1.0 M phosphoric acid, and 1.0 to 2.0 M chromium trioxide while subjected to the action of alternating current at 35.degree. to 55.degree. C.

Etching of aluminum capacitor foil

Aluminum electrolytic capacitor foil is treated prior to anodization in a two-step process in which a hydrous oxide film is first formed on the foil and the hydrous oxide is then modified. In the first step the foil is immersed in boiling water to form an appropriate thickness of hydrous oxide and in the second step it is immersed in a boiling aqueous solution containing phosphate, silicate, or tartrate ions, or combinations thereof. This treatment results in a decreased power consumption during anodization and produces a film having higher film capacitance.

Treating etched aluminum electrolytic capacitor foil

A dielectric oxide film is modified by the incorporation of a minor amount of carbonaceous material. The modified film is produced by anodizing an aluminum electrolytic capacitor anode in a conventional electrolyte containing a minor amount of an alpha- or ortho- hydroxy carboxylic acid or salt.

Anodizing aluminum in boric acid bath containing hydroxy organic acid

Current efficiency is increased in the anodization of aluminum foil for electrolytic capacitors by carrying out the anodization below 90.degree. C. in a non-aqueous ethylene glycol-ammonium pentaborate bath containing a small amount of an orthophosphate source, e.g., ammonium dihydrogen phosphate.

Anodization of aluminum capacitor electrode foil

An electrolytic capacitor is provided with an electrode having a stable aluminum oxide dielectric by anodizing an aluminum foil in a process that includes depolarizing the foil in a bath containing a hydration inhibitor selected from tartrate or citrate or phosphate anions.

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Williamstown, MA, United States of America

John J Randall, Jr