corrosion is the rusting of iron
formation requires iron, oxygen, water
4Fe(s) + 3O2(g) + 2H2O(l) --> 4FeO(OH)
Clearly, without water, there would be no formation of rust.
Redox half-reactions:
Fe(s) + 2H2O --> FeO(OH)(s) + 3H+ + 3e- .... oxidation of iron
3(Fe(s) + O2 + H+ + 1e- --> FeO(OH)) .......... reduction of oxygen
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4Fe(s) + 3O2 + 2H2O --> 2FeO(OH) ....... H+ cancels out, e- cancels out
