| 摘要 |
In anodizing a metal foil strip, as of roughened aluminium, for subsequent use as electrolytic capacitor electrodes, the strip is moved continuously through an anodizing bath or baths with a fixed applied voltage which effects oxidation (forming) and the anodizing process is then interrupted by reducing the applied voltage to a value less than half the initial voltage for a short period, the voltage thereafter being gradually raised until oxidation starts again, forming being continued until a desired residual current is obtained. The voltage may be cut off temporarily but preferably it is merely reduced to a suitable value below that at which oxidation restarts, and is then gradually increased either steadily up to the maximum originally applied or steadily to just above the value at which oxidation restarts and then raised directly to the maximum value. The foil which typically passes between or through the counter-electrodes which are earthed may remain in the bath or be removed from the bath between the two oxidation stages, or two separate baths may be employed. Devices for ensuring the increasing applied voltage of the second stage may comprise funnel shaped electrodes extending downwardly through the bath surface; electrodes covered with insulation arranged to extend downwardly in V formation through the bath surface and to which voltage pulses are applied, bath liquid being fed downwardly through them; insulating barriers immersed in the bath or extending through the bath surface to restrict access of electrolyzing current to the foil which thereafter passes between immersed parallel electrodes, electrolyte being flowed downwardly between them; or slit orifices for directing electrolyte in counter-flow to the direction of foil movement as it passes to the entry of a pair of electrodes. |
