A galvanic anode, a kind of sacrificial anode, is one of the primary parts of a galvanic cathodic defense system utilized to protect metals from corrosion, by the use of a metal electrode which is itself eaten rather in an anodic oxidation response.
For example, pipelines made from steel will wear away because the metal is inhomogeneous in composition, e.g. at the welded joints. An electrochemical cell is formed with two various metals in electrical contact and an electrolyte solution: when it come to a pipeline, moisture and salts around the pipeline function as the electrolyte. As a result of electrical existing flow, the more electronegative metal will slowly be liquefied with the manufacturing of favorable ions. Since this process is a basic home of the materials included, it can not be stopped extremely easily. Nonetheless, it can be diverted, so that far less important metal items are worn away instead. This is the galvanic anode: the pipeline is electrically connected at periods to buried plates of magnesium. Magnesium has a much more adverse electrode potential than iron (-2.37 V for magnesium, versus -0.44 V for iron; see Table of basic electrode capacities) and so will form the anode (unfavorable electrode) of the cell.
Now the electrochemical corrosion does not take location on the costly steel pipeline but rather on the economical magnesium plate, which is slowly transformed into magnesium ions.
Zinc and zinc alloys are commonly made use of for galvanic anodes, for instance in salt-water cooled marine engines and on yacht propellers. Galvanization (or galvanizing) is the process of finish steel with zinc, which then forms both a protective layer and a galvanic anode.
In order to keep their efficiency, galvanic anodes need to be replaced at routine periods as they are eaten. A typical design life for a galvanic anode CP system is 20 years.
Cathodic Protection with Galvanic Anodes – Theory of Cathodic Protection with Galvanic Anodes