At a particular spot
(Fig 2 13) of an object made of iron,
oxidation takes place and that spot
behaves as anode and we can write
the reaction
Anode: 2 Fe (s) ¾® 2 Fe2+ + 4 e– 
o
(Fe2+
/Fe)
E
 = – 0 44 V
Electrons released at anodic spot move through the metal and go
to another spot on the metal and reduce oxygen in the presence of H+
(which is believed to be available from H2CO3 formed due to dissolution
of carbon dioxide from air into water