Editing Anode (section)

==Sacrificial anode==
{{main|Sacrificial anode}}
[[File:Anodes-on-jacket.jpg|thumb|left|[[Sacrificial anode]]s mounted "on the fly" for corrosion protection of a metal structure]]

In [[cathodic protection]], a metal anode that is more reactive to the corrosive environment than the metal system to be protected is electrically linked to the protected system. As a result, the metal anode partially [[corrosion|corrodes]] or dissolves instead of the metal system. As an example, an [[iron]] or [[steel]] [[hull (watercraft)|ship's hull]] may be protected by a zinc [[sacrificial anode]], which will dissolve into the seawater and prevent the hull from being corroded.  Sacrificial anodes are particularly needed for systems where a [[electrostatics|static charge]] is generated by the action of flowing liquids, such as pipelines and watercraft. Sacrificial anodes are also generally used in tank-type water heaters.

In 1824 to reduce the impact of this destructive electrolytic action on ships hulls, their fastenings and underwater equipment, the scientist-engineer [[Humphry Davy]] developed the first and still most widely used marine electrolysis protection system. Davy installed sacrificial anodes made from a more electrically reactive (less noble) metal attached to the vessel hull and electrically connected to form a cathodic protection circuit.

A less obvious example of this type of protection is the process of [[galvanise|galvanising]] iron.  This process coats iron structures (such as fencing) with a coating of [[zinc]] metal.  As long as the zinc remains intact, the iron is protected from the effects of corrosion. Inevitably, the zinc coating becomes breached, either by cracking or physical damage. Once this occurs, corrosive elements act as an electrolyte and the zinc/iron combination as electrodes. The resultant current ensures that the zinc coating is sacrificed but that the base iron does not corrode. Such a coating can protect an iron structure for a few decades, but once the protecting coating is consumed, the iron rapidly corrodes.{{Citation needed|date=February 2024}}

If, conversely, tin is used to coat steel, when a breach of the coating occurs it actually accelerates oxidation of the iron.{{Citation needed|date=February 2024}}