The Corrosion of Iron
About 25% of the steel produced in the United States is made just to
replace steel already in use that has corroded. Rust arises through a
complex electrochemical process.
1) Iron does not rust in dry air: moisture must be present.
2) Iron does not rust in air-free water: oxygen must be present.
3) The loss of iron and the deposition of rust often occur at different
places on the same object.
4) Iron rusts more quickly at low pH (high [H+]).
5) Iron rusts more quickly in contact with ionic solutions.
6) Iron rusts more quickly in contact with a less active metal (such as
Cu) and more slowly in contact with a more active metal (such as Zn).
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