| Corrosion
as an Electromechanical Process |
| A piece of bare
iron left outside where it is exposed to moisture
will rust quickly. It will do so even more quickly
if the moisture is salt water. The corrosion
rate is enhanced by an electrochemical process
in which a water droplet acts like a voltaic
cell in contact with the metal, oxidizing the
iron. |
 |
| The problem
with iron as well as many other metals is that
the oxide formed by oxidation does not firmly
adhere to the surface of the metal and flakes
off easily causing "pitting". Extensive
pitting eventually causes structural weakness
and disintegration of the metal. (It should
be noted, however, that certain metals such
as aluminum, form a very tough oxide coating
which strongly bonds to the surface of the metal
preventing the surface from further exposure
to oxygen and corrosion). |
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