What is metallic corrosion ? Explain it with respect to iron corrosion.

Explanation

Metallic corrosion: The natural tendency of conversion of a metal into its mineral compound form on interaction with the environment is known as metallic corrosion.
Eg.: 1) Iron converts itself in its oxide [Resting] `(Fe_(2)O_(3))`
2) Silver converts itself into it's sulphate [tarnishing] `[Ag_(2)S]`
Rusting of iron: Iron converts it self into its oxixe `Fe _(2)O_(3)`
The electrochemical reaction that represents the corrosion or rusting of iron is
Anode `:2Fe_((s))to 2 Fe ^(2+)+4e^(-)" "E_((Fe^(2+)//Fe))=-0.44V`
Cathode `: O_(2_((g)))+4H_((aq))^(+)4e^(-)to 2H_(2)O_((l))" "E_(H^(+)//O_(2)//H_(2)O)^(Θ)=1.23V`
Overall reaction `: 2 Fe_((s))+O_(2_((g)))+4H_((aq))^(+)to 2Fe_(aq)^(+2) +2H_(2)O_((l))" "E_((cell))^(Θ)=1.67V`