HOW DOES RUST FORM
HOW DOES RUST FORM
Rust forms due to the reaction of oxygen dissolved in water with iron. Rust is a generic term to describe different oxides, Fe(OH)2, Fe(OH)3, FeO(OH), Fe2O3.H2O that form when iron corrodes.
The common form of Rust is a Red products:Fe2O3.
The oxygen in the air dissolves in the water and causes rust to form. There are always two distinct chemical reactions in a corrosion process, the basic chemistry of corrosion is:
1) Anodic Dissolution of Metal (Iron) that goes into solution (water)
Fe -----> Fe2+ + 2e-
2) Cathodic Reduction of Oxygen dissolved into water
O2 + 2H2O + 4e- ----> 4OH-
The final reaction is: Fe2+ + 2OH- -----> Fe(OH)2
This oxide will then further reacts with oxygen to give the final red product:Fe2O3.H2O
Corrosion of Metals
The corrosion of metals is an electrochemical process. That is, it is an electrical circuit where the exchange of electrons (electricity) is conducted by chemical reactions in part of the circuit. These chemical reactions occur at the surface of the metal exposed to the electrolyte. Oxidation reactions (corrosion) occur at the surface of the anode and reduction reactions occur at the surface of the cathode.
Corrosion metal definition
There are different corrosion metal definition, but the basic principle is the same: an interaction of the metal with its environments. These are some example of corrosion metal definition:
What causes corrosion
As seen above a Corrosion process is the results of the interaction of a metals with its environments. Usually what causes corrosion, at least what we can see in our daily life, is what is called "wet" corrosion. "Wet" corrosion means that there is a water phase, humidity, rain, seawater..., in contact with the metal surface. So what causes corrosion is the interaction of the water, or better the oxygen dissolved in the water, through the reactions seen above, with the metal.
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