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  for Metal Finishing since 1989
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Oxidation of different metals

Dear Sir,

I am a middle school student and am doing my 8th grade science fair project. My topic is on which chosen metals are the fastest. I chose copper, galvanized steel, ungalvanized steel (black), and aluminum. The liquid I chose to put them in was tap water. So far the only one that rusted was the ungalvanized steel. I didn't really expect the copper to rust, but it did turn a little green. And the aluminum grew some type f white thing on all different parts of it. The galvanized steel just turned the water a little dirty but that's it. Please tell me if the copper, aluminum, and galvanized steel will rust and if a different liquid can speed up the process. Thank you.

P.S. I read somewhere that copper cannot oxidate in any organic liquids. Does that include tap water?

Kyle P.
student - Sylmar, California, United States of America
2005

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Kyle, not all "rusts" are brown like we see on iron. Rust is actually the oxide or hydroxide of the metal, so aluminium will oxidise (or rust) to give a white deposit; zinc does a similar thing. Galvanised steel is actually steel (iron) coated with zinc; it has excellent corrosion properties but the reasons for it are quite complicated. Copper will not react with water unless there are other things in it and since you have used tap water, there will be other things there. That is why it turned slightly green. As far as copper reacting with organic liquids such as water - water is not an organic liquid and there are some organic materials that will react with copper. Enjoy your experiments and enjoy learning about science. One of the best things is trying to explain what you have seen!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2005