Advanced Topic 588 of 1102 Acids, Bases & Electrochemistry
Sacrificial Anode
A more reactive metal such as zinc or magnesium corrodes in place of iron.
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In-depth explanation of Sacrificial Anode
A sacrificial anode is a more reactive metal such as magnesium, zinc or aluminium that is electrically connected to a structure of iron or steel. The more reactive metal corrodes preferentially and supplies electrons to the iron, which therefore remains in its reduced state and does not corrode. The sacrificial metal is gradually consumed and must be replaced periodically. The method works because the standard potential of the more reactive metal is more negative than that of iron. It is widely used on ship hulls, buried pipelines and water heaters.
Going deeper: Sacrificial Anode
Key ideas: A more active metal (Mg, Zn, Al) is connected electrically to the structure and corrodes instead of it. It works because its reduction potential is lower than iron's (Mg -2.37 V, Zn -0.76 V, Fe -0.44 V). Used on ship hulls, pipelines, water heaters (Mg rod) and offshore rigs. Anodes must be replaced as they are consumed.
Common mistakes and connections: Mistakes: using a less active metal like Cu, which accelerates iron corrosion, and failing to maintain electrical contact. The anode needs to be in the same electrolyte. Mass consumed follows Faraday law, which is used to size the anode for a design life. Also called cathodic protection.
Visualization of Sacrificial Anode
A magnesium block bolted to steel has a more negative potential than iron, so it corrodes first and supplies electrons that keep the iron intact. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A zinc block bolted to a steel ship hull corrodes in preference to the steel, which stays protected.
Frequently asked questions about Sacrificial Anode
What is Sacrificial Anode?
A more reactive metal such as zinc or magnesium corrodes in place of iron.
Is Sacrificial Anode a beginner, intermediate or advanced topic?
Sacrificial Anode is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Sacrificial Anode?
Study these earlier topics in Acids, Bases & Electrochemistry first: Corrosion, Rusting of Iron, Prevention of Corrosion.
What comes after Sacrificial Anode?
The next topics in Acids, Bases & Electrochemistry are Galvanization and Conductance and Conductivity.
Can I practise Sacrificial Anode with quizzes?
Yes. The interactive lesson includes a self-check question on Sacrificial Anode, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Sacrificial Anode fits in Acids, Bases & Electrochemistry
Sacrificial Anode is topic 78 of 105 in Acids, Bases & Electrochemistry.