Electrode Whewell at Faraday's request). The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs (indicated by a minus symbol, "−"), and the cathode as the electrode at which electrons enter the cell and reduction occurs (indicated by a plus symbol, "+"). Each electrode may become either the anode or the cathode depending on the direction of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell and the cathode of another cell. A primary cell is a special type of electrochemical cell in which the
SAL electrolytic capacitor 31, 2015 these are now end-of-life and have ceased production. Basic anode material of solid aluminum capacitors exists of highly purified aluminum with a purity of at least 99.99%. In an electrochemical process the anode material is etched (roughened) to increase the effective electrode surface. After that the roughened aluminum becomes oxidized or formed by an anodic oxidizing process. Thereby an electrical insulating oxide layer AlO is formed on the aluminum surface by applying an electric current in correct polarity in an electrolytic bath. This process of oxide formation is carried out into two reaction steps: The aluminum oxide layer