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Name: j gordon
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1999
Question:
Why does salt water make metals corrode faster?


Replies:
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.

christopher grayce


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