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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Does different environment effect the results of rusting?
Q. HI, I'm Sachu. I'm a high school student in Year 10. I'm working on a experiment on testing which method is the effective way from iron to stop rusting. I've set them up in different environments i.e. tap water, distilled and salt water. I want to know why does the metal coated with zinc rust more in tap water than in distilled?
Your early reply would be appreciated.
Sachu G. [surname deleted for privacy by Editor]
student - Australia
2007
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A. Hi Sachu,
Well, distilled water implies perfect l00% water less any salts or alkalies ... here in White Rock our well water measures 7.88 pH ... pH, as you know or should know, is at zero at 7.00 ... and we sure don't use bottled water due to its lack of impurities and of chlorine.
Hence tap water contains impurities and perhaps some chlorination which sure can advance corrosion.
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2007
A. First, the nail can not rust if it has zinc still on it. The tap water contains chlorine which will turn the water slightly acidic and eat the zinc coating off of the nail if the coating is thin (electroplated and not coated with glue or a clear coat). Galvanized nails have a very thick zinc coating and will be very slow to show rust.
Next, there are various salts in tap water which will aid in the conductivity and the electron transfer for both the de-zincing and the formation of rust. High quality distilled water has none of these problems.
It will still eventually rust, but normally it will be a lot slower. Your experiment is testing the effectiveness of the zinc coating and only a very very tiny bit of testing the rusting of a nail.
James Watts
- Navarre, Florida
2007
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