Blog 5 1/24/11 Corrosion Process

Corrosion of Iron


1) Fe -> + Fe2+ + 2e-Fe2+ is Positive Iron Ion
e- is Electron


1) Iron molecules give up electrons in the presence of water and oxygen dissolved into the water. This iron that lost electrons is positively charged. This is called positive iron ion, and they dissolve in the electrolyte.

2) O2 + 2H2O + 4e- -> 4OH-
O2 is Oxygen
H2O is Water
e- is Electron
OH- is Negative Hydroxide

2) The electrons move through the iron from the anode to the cathode, where hydroxide with a negative charge is formed through the chemical reaction of water, dissolving oxygen and the electrons.

3) Fe2+ + 2OH--> Fe(OH)2
Fe2+ is Positive Iron Ion
OH- is Negative Hydroxide
Fe(OH)2 is Ferrous Oxide

3) Ferrous hydroxide is formed when there is a chemical reaction between the negatively charged hydroxide reacts with positive iron ion in the electrolyte, and that ferrous oxide forms on the iron surface from the electrolyte.

4) 4Fe(OH)2 + O2 -> 2Fe2O3 •H2O + 2H2O
O2 is Oxygen
Fe(OH)2 is Ferrous Oxide
2Fe2O3 •H2O is Rust
H2O is Water

4) In the presence of water and oxygen, ferrous hydroxide is extremely unstable and it forms rust with another chemical reaction with the water and dissolved oxygen.

(Wen-Yi Ouyang, Personal Communication, January 23, 2011)