Question

The corrosion of metal by galvanic cell action takes place due to the presence of impurities which are​

Answer 1

Answer:

Explanation:Galvanic corrosion (also called ' dissimilar metal corrosion' or wrongly 'electrolysis') refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte. It occurs when two (or more) dissimilar metals are brought into electrical contact under water. When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would all by itself, while the other becomes the cathode and corrodes slower than it would alone.

                   

Answer 2

The corrosion of metal by galvanic cell action takes place due to the presence of several impurities. Let us see more about this in the following points :

• In electrochemical corrosion. the metal undergoing corrosion acts as an anode.
• In anode region, the metal is oxidized to metal cation and in cathode region, oxygen is reduced to water.
• Galvanic corrosion (also called ' dissimilar metal corrosion' or wrongly 'electrolysis') refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte.
• It occurs when two (or more) dissimilar metals are brought into electrical contact under water.
• When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would all by itself, while the other becomes the cathode and corrodes slower than it would alone.
• Either (or both) metal in the couple may or may not corrode by itself (themselves). When contact with a dissimilar metal is made, however, the self corrosion rates will change.
• Corrosion of the anode will accelerate .
• Corrosion of the cathode will decelerate or even stop.
• Galvanic coupling is the foundation of many corrosion monitoring techniques

Numerous examples of galvanic corrosion are encountered as it is one of the most frequently encountered forms of corrosion. The following are common examples:

(1) Galvanic corrosion of aluminum shielding in buried telephone cables.

(2) Galvanic corrosion of steel pipe with brass fittings.

(3) Galvanic corrosion of the body of the ship in contact with brass or bronze propellers.

(4) Galvanic corrosion on a gannet wheel where the steel securing the bolts is in contact with the magnesium wheel.

(5) Galvanic corrosion between the tubes and the tube sheet in heat exchangers.

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