Patent ID: 8535507

Claim:
A method for creating a plurality of porous anode foils, comprising: electrochemical drilling a plurality of etched metal foils in sequence one after the other, in a bath containing electrochemical drilling (ECD) solution initially having comprising 10 to 5000 PPM of a surface passivator and about 0.1% by weight of an acid, wherein the ECD solution has a pH within a range of 0.5 to 3, and further wherein said electrochemical drilling step includes: adding ECD replenishment solution having comprising 10 to 5000 PPM of the surface passivator and about 0.1% by weight of an acid, wherein the ECD replenishment solution has a pH within a range of 0.5 to 3, to the bath at such a rate so as to maintain the pH in the ECD solution; and discharging solution from the bath at substantially the same rate as the ECD replenishment solution is added to the bath.