Patent ID: 7578924

Claim:
A method of etching an aluminum anode foil, comprising: (a) treating the anode foil in an aqueous electrolyte bath composition comprising a sulfate, selected from the group consisting of sodium sulfate, potassium sulfate, and lithium sulfate, and mixtures thereof, an oxidizing agent comprising sodium perchlorate, and a halide; and (b) passing a direct current (DC) charge through the anode foil while the foil is immersed in the electrolyte bath; such that the anode foil is etched, wherein the DC charge has a current density ranging from about 0.1 A/cm 2 to about 0.2 A/cm 2 , and wherein the electrolyte bath composition comprises sulfate in an amount ranging from about 700 parts per million (ppm) to about 2000 ppm.