More about Anodes

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An anode is a terminal or electrode in an electrochemical cell, battery or circuit. Its role and charge vary based on the application; in an electrochemical cell, oxidation occurs at the anode and in an electrolytic cell, it is the positive terminal. In respect to the battery or cell, an anode is positive; in respect to the external circuit around such a device, it is negative. Anodes also refer to materials used to protect various metals from corrosive environments, as well as to materials used in electroplating operations.

Anodes used in cathodic protection are known as galvanic anodes or sacrificial anodes. They consist of metals like zinc, aluminum and magnesium, because these materials corrode easily, therefore setting up an electrolytic circuit. These anodes are used to protect submerged and buried pipe, ship hulls, water heaters, metal dock components, tanks and similar functions. Impressed current anodes are also used for some of these applications, although they tend to be more expensive than galvanic anodes. A relatively simple example of a sacrificial anode is the zinc anodes attached to crab pots and similar metal marine traps. They simply consist of a piece of zinc that is attached to the zinc-galvanized wire trap; the sacrificial anode forms a galvanic couple with the wire, and corrodes at a faster rate, while slowing the rate of corrosion for the wire, thereby extending its life.

Anodes are also used in plating operations, where they provide electrons to the cathode, through the outer circuit, and supply the electroplating solution with oxidized metal, which dissolves into the solution. In order for an electroplating operation to succeed, the solution must contain a salt of the metal to be deposited; the anode is typically made of the same material, or a combination of that material and others. The anode will slowly dissolve into the solution, and will therefore eventually require replacement.