write electrochemical theory of corrosion I want big ans it is if 5marks question
Answers
Most of the corrosion takes place on the basis of electrochemical reactions on the surface of metal such a type of corrosion is known as wet corrosion.
Electrochemical theory of corrosion can be taking iron as an example.
When a metal like iron is exposed to the environment according to electrochemical theory corrosion of metal takes place due to the formation of anodic and cathodic regions on the same metal surface or when the two metals are in contact with each other in a corrosive medium.
These anodes and cathodes are formed due to the heterogeneities at the interfaces of the metal and environment. The heterogeneities on a metal surface could develop due to several factors like
1. On a metal surface if the concentration of the oxygen is different (if in the metal the area which is exposed to more oxygen acts as cathode, the area which is exposed to less oxygen concentration acts as anode).
2. Due to contact of two different metals (egs: if copper and iron are in contact with each other, then Fe acts as anode and copper acts as cathode due to change in electrode potential).
3. If metal surface subjected to stress (area under stress acts as anode).
Electrochemical corrosion or wet corrosion takes place on the metal when it's exposed to environment in the presence of moisture....
According to this theory...
# Corrosion of metals occurs due to the formation of galvanic cells with anodic and cathodic region all over the metal substance.
# Anodic regions undergoes oxidation forming metal ions and liberating electrons and suffers from corrosion..
# At cathodic region, reduction take place using electrons liberated at the anode..
# Corrosion continuous as long as both anodic and cathodic reactions takes place simultaneously....
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