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What is Corrosion

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What is Corrosion?


In order to understand What is Corrosion and how does it occur, is necessary to understand how corrosion works and why metals are affected by corrosion.


Metals used in the construction, e.g. steel, stainless steel grades, copper alloys, are subject to different types of corrosion, this is due to the high energy content of the elements in metallic form.


In nature, most metals are found in chemical combination with other elements; these metallic ores are refined by man and formed into metals and alloys.


As the energy content of the metals and alloys is higher than that of their ores, chemical re-combination of the metals to form ore like compounds, i.e. the corrosion, is a natural process.



Corrosion of metals takes place through the action of the electrochemical cell. Although this single mechanism is responsible, there are several different types of corrosion possible.



What is the chemistry of Corrosion and How to Prevent Corrosion.


The generic chemistry of corrosion of metals is metal loss at anodic sites is:


M ---> M+ + e-



M = uncharged metal atom at the metal surface

M+ = positively charged metal ion in the electrolyte

e- = electron that remains in the metal



This type of chemical reaction is called metal oxidation.

More than one electron can be lost in the reaction as in the case of iron where the most common anodic reaction is:


Fe ---> Fe2+ + 2e-



Fe = metallic iron


Fe2+= ferrous ion that carries a double positive charge



The electrons that are produced at anodic sites are consumed at cathodic sites. The type of chemical reactions that consume electrons are called reduction:


One of the most common cathodic reaction is the reduction of oxygen:


O2 + 4e- + 4H2O ---> 4OH-





iron corrosion, mechanism of iron corrosion


How to prevent corrosion


The most common method that is used to prevent corrosion of metals is the application of coating or paint of the metal surface in order to avoid the contact between the metal and the environment.


see also:


Corrosion Control Methods


What is Rusting?


Corrosion Types


Metal Rust Remover


What is the best Rust Remover?


What causes rust?


Galvanic Corrosion