What is electro chemical corrosion and waht are its management ways? answer in detail.?

Question

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Answer 1

Corrosion is largely an electro chemical phenomenon and is liable to occur whenever a difference in potential exists between two metals or a metal and substances in its vicinity in the presence of an electrolyte. it can also occur when a difference in potential exists between separate regions of a single piece of metal or between the difference constituents of an alloy. The degree of corrosion experienced will depend on external conditions and in some environments will be negligible; serious attack usually takes place only if moisture is present to act as an electrolyte between the poles created by any difference in potential. Two changes the occur, the metal that is attacked suffers a chemical change, some of it being converted into a metallic compound, whilst the cathodic pole of the circuit may be reduced

Answer 2

Electrochemical Corrosion Theory:

Electrochemical corrosion involves two half-cell reactions; an oxidation reaction at the anode and a reduction reaction at the cathode. For iron corroding in water with a near neutral pH, these half cell reactions can be represented as:

Anode reaction: 2Fe => 2Fe2+ + 4e-

Cathode reaction: O2 + 2H2O + 4e- => 4OH-

There are obviously different anodic and cathodic reactions for different alloys exposed to various environments. These half cell reactions are thought to occur (at least initially) at microscopic anodes and cathodes covering a corroding surface. Macroscopic anodes and cathodes can develop as corrosion damage progresses with time.

From the above theory it should be apparent that there are four fundamental components in an electrochemical corrosion cell:

1-An anode.

2-A cathode.

3-A conducting environment for ionic movement (electrolyte).

4-An electrical connection between the anode and cathode for the flow of electron current.



If any of the above components is missing or disabled, the electrochemical corrosion process will be stopped. Clearly, these elements are thus fundamentally important for corrosion control.

you can control this type of corrosion by

1-Cathodic protiction which is achieved by placing in contact with the metal to be protected another more easily corroded metal to act as the anode of the electrochemical cell

2-Anodic protection by reduction of the corrosion rate in an anode by polarizing (passivateing) it into a potential region.