Sacrificial metal

A sacrificial metal is a metal used as a sacrificial anode in cathodic protection that corrodes to prevent a primary metal from corrosion, galvanization or rusting.

When two metals touch each other and water is present, electrolysis occurs. One well known example is the reaction between zinc (Zn) and iron (Fe). Zn atoms ionize as it is more electronegative and is oxidized and corrodes.

Zn(s)→Zn2+
(aq) +2e (oxidation)

Sacrificial metals are widely used to prevent other metals from rusting, for example food cans. Most of the food can is coated with a layer of metal that is more electronegative than the metal (mostly iron) inside the food can, preventing the iron contaminating the food with Fe2+
ions. They can also be attached to the hull of a ship to prevent it from rusting and breaking down. They are also used in oil rigs to stop the frame of the rig from rusting.

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