Rusting process??

The process of rusting involves a series of chemical reactions.

The first stage involves 3 steps:

(1) Iron lose electrons to become Iron (II) ions:
Fe (s) => Fe2+ (aq) + 2 e−

(2) Dissolved oxygen in water accepts the electrons and becomes hydroxide ions:
O2 (aq) + H2O (l) + 4e− => 4OH− (aq)

(3) Iron (II) ions and hydroxide ions react in water to form Iron (II) hydroxide (insoluble, green precipitation)
Fe2+ (aq) + 2OH− (aq) => Fe(OH) 2 (s)

Overall equation for 1-3: 2Fe(s) + O2 (aq) + H2O (l) => 2Fe(OH) 2 (s)

(4) Iron (II) hyrdoxide is then further oxidized by dissolved oxygen to Iron (III) hydroxide:
Fe(OH) 2 (s) + O2 (aq) + 2H2O(l) => 4Fe(OH) 3 (s)

(5) Iron (III) hydroxide will further change to its hydrated form:
Fe2O3·nH2O(s) (hydrated Iron(III) oxide = Rust, a reddish brown solid)

Water and oxygen gas will react to give out hydroixe ion:
2H20 + O2 + 4e- --> 4OH-
so the iron will lose electron to complete the reaction;
Fe --> Fe3+ + 3e-
Overall Reaction:
6H2O + 3O2 + 4Fe -->4Fe(OH)3

then iron(III)hydroxide will rearrange themself to hydrated iron(III)oxide:

2Fe(OH)3 --> Fe2O3‧3H2O

2007-03-03 23:41:39 補充：
sorry, 記錯佐,應該係:Fe → Fe2 2e− 4e− O2 2H2O → 4OH− Fe2 2OH− → Fe(OH)2 4Fe(OH)2 O2 → 2(Fe2O3.xH2O) 2H2O

3Fe + nH2O + 2O2 --> FeO.Fe2O3.nH2O