Cleaning and treatment of etched cathode aluminum capacitor foil

Claim 2

A process for post etch treatment of a running length of electrolytically etched cathode aluminum capacitor foil to remove chlorides from the etched surface and increase capacitance of the foil comprising the steps of passing the etched foil through a first post etch treatment bath comprising an aqueous solution of nitric acid, rinsing the nitric acid solution from the surface of the foil, passing the foil through a second post etch treatment bath comprising an aqueous solution of chromic acid and phosphoric acid, and rinsing the chromic acid and phosphoric acid solution from the surface of the foil.

Claim 3

The process defined in claim 1 wherein said first treatment bath comprises nitric acid in the amount of about 2.5 to about 3.7 weight percent.

Claim 4

The process defined in claim 2 wherein said first treatment bath is maintained at a temperature within the range of about 45° C. to about 55° C.

Claim 5

The process defined in claim 1 wherein said second treatment bath comprises chromic acid in the form of CrO 3 within the range of about 1.5 to about 5.0 weight percent.

Claim 6

The process defined in claim 1 wherein said second treatment bath comprises phosphoric acid within the range of about 3.0 to about 5.0 weight percent.

Claim 7

The process according to claim 1 wherein said first treatment bath comprises nitric acid within the range of about 2.5 to about 3.7 weight percent and wherein said second treatment bath comprises chromic acid in the form of CrO 3 within the range of about 1.5 to about 5.0 weight percent and phosphoric acid within the range of about 3.0 to about 5.0 weight percent.

Claim 8

The process defined in claim 6 wherein the temperature of said first treatment bath is maintained within the range of about 45° C. to about 55° C. and wherein the temperature of said second treatment bath is maintained within the range of about 80° C. to about 100° C.

Claim 9

The process defined in claim 7 wherein said electrolytically etched cathode aluminum foil is immersed in each of said first and said second treatment baths for a time within the range of about 25 to about 60 seconds.

Claim 10

The process defined by claim 1 further comprising the step of passivating said electrolytically etched cathode aluminum foil by passing the foil through a third treatment bath comprising an aqueous solution of a carboxyl acid for a time within the range of about 25 to 110 seconds, and drying the foil following withdrawal from the third treatment bath.

Claim 11

The process according to claim 9 wherein said third treatment bath comprises an aqueous solution of citric acid.

Claim 12

The process defined in claim 10 wherein said third treatment bath comprises about 1.8 to about 5.0 weight percent citric acid, balance deionized water, and wherein the passivation bath is maintained at a temperature within the range of about 45° C. to about 55° C.

Claim 13

In a process for producing cathode aluminum capacitor foil in which a running length of aluminum foil of about 98.0% to about 99.99% pure aluminum is electrolytically etched in a liquid electrolyte comprising hydrochloric acid, nitric acid and phosphoric acid in water solution while applying an electric current to electrodes immersed in the electrolyte solution in spaced relation to the foil, the improvement comprising the steps of water washing the running length of foil promptly upon withdrawal from the electrolyte solution to remove electrolyte solution and chlorides produced in the electrolytic etching process from the surface of the foil, passing the rinsed, etched foil through a first post etch treatment bath comprising an aqueous solution of nitric acid, rinsing the nitric acid solution from the surface of the foil promptly upon withdrawing the foil from the first post etch treatment bath, passing the washed foil through a second post etch treatment bath comprising an aqueous solution of chromic acid and phosphoric acid, and rinsing the chromic acid and phosphoric acid solution from the surface of the foil promptly upon withdrawal from the second post etch treatment bath.

Claim 14

In a process for producing cathode aluminum capacitor foil in which a running length of aluminum foil of about 98.0% to about 99.99% pure aluminum is electrolytically etched in a liquid electrolyte comprising hydrochloric acid, nitric acid and phosphoric acid in water solution while applying an electric current to electrodes immersed in the electrolyte solution in spaced relation to the foil, the improvement comprising the steps of water washing the running length of foil promptly upon withdrawal from the electrolyte solution to remove electrolyte solution and chlorides produced in the electrolytic etching process from the surface of the foil, passing the rinsed, etched foil through a first post etch treatment bath comprising an aqueous solution of nitric acid, rinsing the nitric acid solution from the surface of the foil promptly upon withdrawing the foil from the first post etch treatment bath, passing the washed foil through a second post etch treatment bath comprising an aqueous solution of chromic acid and phosphoric acid, and rinsing the chromic acid and phosphoric acid solution from the surface of the foil promptly upon withdrawal from the second post etch treatment bath.

Claim 15

The process defined in claim 12 wherein deionized water is used to rinse the foil following withdrawal from said first and said second post etch treatment baths.

Claim 16

The process defined in claim 13 wherein said first post etch treatment bath is maintained at a temperature within the range of about 45° C. to about 55° C. and comprises nitric acid in the amount of about 2.5 to about 3.7 weight percent, and said second post etch treatment bath is maintained at a temperature within the range of about 80° C. to about 100° C. and comprises CrO 3 within the range of about 1.5 to about 5.0 weight percent and H 3 PO 4 within the range of about 3.0 to about 5.0 weight percent.

Claim 17

The process defined in claim 14 wherein said electolytically etched cathode aluminum capacitor foil is immersed in each of said first and said second treatment baths for a time within the range of about 25 to about 60 seconds.

Claim 18

The process defined in claim 15 further comprising the steps of passivating said electrolytically etched cathode aluminum capacitor foil by passing the foil through a third post etch treatment bath comprising an aqueous solution of a carboxyl acid for a time within the range of about 25 to about 110 seconds, and drying the etched, treated and passivated foil following withdrawal from the third post etch treatment bath.

Claim 19

The process according to claim 16 wherein said third post etch treatment bath is maintained at a temperature within the range of about 45° C. to about 55° C. and comprises an aqueous solution of citric acid containing about 1.5 to about 5.0 weight percent citric acid.