Salt water corroding metals
Name: j gordon
Why does salt water make metals corrode faster?
Metals corrode because electrons are stolen from or donated to them by
other compounds in the neighborhood, typically other metals. When the
electrons are stolen or added, the metal atoms become charged and will
dissolve in the water. Naturally the process works better if the water
conducts electricity well so that the electrons can come from far away
sources as well as nearby. Salt water conducts better than fresh.
This is the simplest situation. Some metals form compounds with things
dissolved in the water, and this surface layer may protect them from
further reactions. People with boats, incidentally, often put
"sacrificial" pieces of aluminum near propellor shafts and suchlike because
aluminum tends to be eaten away in preference to iron. Also, in the
deep ocean bacteria eat iron and excrete it as rust.
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Update: June 2012