Galvanic Corrosion

Sacrificial anodes

What is Galvanic Corrosion?

Galvanic Corrosion is an electrical-chemical process where one of the metals are more likely to corrode than the other, when both metals are linked electrically.

Anodes ( sacrificial anodes ) when used to protect various steel strucutures is a good example of galvanic corrosion. That is when the anode corrodes to protect the structure.

Protection Against Galvanic Corrosion With Sacrificial Anodes

One type of cathodic protection system in order to prevent galvanic corrosion, is the sacrificial anode. The anode is made from a metal alloy with a more "active" voltage (more negative electrochemical potential) than the metal it’s protecting (the cathode). This means that the sacrificial anode material corrodes in preference to the structure. This effectively stops the oxidation reactions on the metal of the structure being protected.

There are two additional conditions that needs to exist in order for the sacrificial anode method to work.

  • There must be a return current path ( a current path connecting the anode and the cathode )
  • An electrolyte ( water, soil, etc ) to convey the electrons.

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