Editing Corrosion (section)

==== Sacrificial anode protection ====
[[File:Sacrificial anode.jpg|thumb|Sacrificial anode attached to the hull of a ship]]
For effective CP, the potential of the steel surface is polarized (pushed) more negative until the metal surface has a uniform potential. With a uniform potential, the driving force for the corrosion reaction is halted. For galvanic CP systems, the anode material corrodes under the influence of the steel, and eventually it must be replaced. The [[polarization (corrosion)|polarization]] is caused by the current flow from the anode to the cathode, driven by the difference in [[electrode potential]] between the anode and the cathode. The most common sacrificial anode materials are aluminum, zinc, magnesium and related alloys. Aluminum has the highest capacity, and magnesium has the highest driving voltage and is thus used where resistance is higher. Zinc is general purpose and the basis for galvanizing.

A number of problems are associated with sacrificial anodes. Among these, from an environmental perspective, is the release of zinc, magnesium, aluminum and heavy metals such as [[cadmium]] into the environment including seawater. From a working perspective, sacrificial anodes systems are considered to be less precise than modern cathodic protection systems such as Impressed Current Cathodic Protection (ICCP) systems. Their ability to provide requisite protection has to be checked regularly by means of underwater inspection by divers. Furthermore, as they have a finite lifespan, sacrificial anodes need to be replaced regularly over time.<ref>{{cite web|url= https://www.hydrosolution.com/en/guide-and-tips/the-sacrificial-anode-what-is-it-and-when-should-you-replace-it/|title= The sacrificial anode: what is it? When should you replace|author= <!--Not stated-->|date= 20 January 2020|website= hydrosolution.com|publisher= Hydro Solution|access-date= 2022-09-13|quote= Most water heater manufacturers will recommend inspecting the condition of the sacrificial anode every one (1) to three (3) years and replacing it when it has been consumed more than 50%|archive-date= 2022-09-13|archive-url= https://web.archive.org/web/20220913050416/https://www.hydrosolution.com/en/guide-and-tips/the-sacrificial-anode-what-is-it-and-when-should-you-replace-it/|url-status= live}}</ref>