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What is an Aluminum Anode?

H. Bliss
H. Bliss

When used as part of a technique called cathodic protection (CP), an aluminum anode is a conductive rod that is attached to metal structures or installed into metal devices. This part is used to reduce corrosion in metal objects including buildings, structures, and home appliances like water heaters. Because an anode is the current-discharging contact point in an electrical system, the term can also be used to refer to the negative end of some types of non-rechargeable battery.

Corrosion is a chemical process that slowly degrades metal. This process occurs as a result of reaction between a metal object and its surrounding environment, and becomes more severe underwater or in wet environments. Over time, corrosion can damage a structure enough to threaten its stability, so engineers often take anti-corrosion steps to prevent degradation of metal structures. One of these is placing one or more aluminum anode rods in or near corrosion-prone areas, making the aluminum anode a sacrificial anode for a metal structure, in a process called cathodic protection.

Man holding computer
Man holding computer

Cathodic protection is a process used to keep metal structures from corroding in liquid. It works because a more corrosive metal, when placed next to a less corrosive metal, will corrode in its stead. This technology is frequently used for boats, bridges and other metal structures that have contact with water because it increases the life of the structure by ensuring that the metal stays strong for a longer period of time.

Usually, cathodic protection is used in combination with other anti-corrosion techniques like galvanization. Besides aluminum, other materials used for cathodic protection in industry include zinc and graphite or carbon. The closer the sacrificial rod is placed to the protected metal, the more effective it will be in reducing corrosion in the area surrounding the sacrificial rod.

Though an aluminum anode is used frequently as cathodic protection in manufacturing and industrial applications, it is most commonly seen in the home as a sacrificial anode for a common water heater. An aluminum anode in a water heater extends the life of the water heater by preventing corrosion. Over time, the sacrificial aluminum anode becomes corroded and needs to be replaced to continue protecting the water heater from corrosive damage.

Less frequently, the anode end on aluminum battery can be called an aluminum anode. On a common battery, the anode is the end that sends the current out to the device. Visually, the anode end of a battery appears slightly indented, in contrast with the positive cathode end of the battery, which protrudes slightly, like a nubby pencil eraser.

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