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Rate of penny corrosion
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Our lab is currently conducting experiments on the nature of acid corrosion on the 1989 U.S. penny. In one of our tests, we are submerging the penny in 300 ml of coca-cola, in an Ehrlenmeyer flask, and measuring change over time. My question is, do you know of any empirically supported documentation showing the rates of corrosion and/or at what rate the penny will actually dissolve (if at all)?
Thank you,
Kevin J. [last name deleted for privacy by Editor]microbiologist - Los Angeles, California
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Hi, Kevin. I can't decide if you are a high school kid posing your question in this style to try to trick us into doing your homework for you, or if you are honestly doing real research.
Why 1989 pennies rather than 1988 or 1990? What would make them different?
Why coca-cola, which is a hodgepodge of secret ingredients, and whose acidity is supported by volatile carbonic acid, rather than a repeatable, documentable acid like .01 N HCl or something? If forced to bet, I'm going with high school homework.
After you do your trials, let us know what corrosion rate you got.
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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Will you see some long term attack on the penny, Yes. Far too much depends on how clean the penny was when you started (oxides, grease and etc) , the temperature that it is kept at, the amount of agitation, can the coke effectively get to both sides, how often are you cleaning the resulting smut off of the penny, the effect of the increasing sugar content as it slowly evaporates. TOO many variables and no one cares enough to document(publish) the results if they had done any work. Coke certainly is not going to talk about it. If you want a real life shock, put a 1" cube of lean steak in the same 300 mL of Coke and put cover on the flask or beaker.
James Watts- Navarre, Florida
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dude I need to know about how long it takes for the penny to show a change.
Katherine R. [last name deleted for privacy by Editor]- Austin, Texas
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As long as it takes an hour hand to move, Katherine. How big a change? How long have your coins been immersed without showing any change?
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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My daughter is in 3rd. grade and would like to do her science project on the corrosion of a penny she's 9 yrs. so this is new for us, I am trying to help her and we thought we would put the pennies in small cups with some general items she can work with such as water, Coke, lemon juice, bleach, and maybe hydrogen peroxide [linked by editor to product info at Amazon]. I will have her watch the changes and note what takes place first. Am I on the right track? Any other liquids you could suggest would help and do I need to cover the cups? And she only has three weeks is this long enough? Thanks so much for all the help you can provide.
Christina D. [last name deleted for privacy by Editor]student - Swartz Creek, Michigan
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Hi I'm in 8th grade I'm doing a science fair project on penny corrosion my question is as followed.
My question is for my science fair I'm doing a project on which penny corrodes faster in coke-cola, lemon juice, and orange juice. I was thinking of putting the pennies into 3 different cups each filled with 3 tablespoons and the 3 different liquids into each cup. I am going to try and time the amount of time it takes for each penny to corrode.I will check on it every 5 min stopping at 15 min. Is that too short of time? well please get back to me as soon as possible. thank you.
Student - Chicago, Illinois
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You're doing fine, Christina. Cover the cups if you expect the test to last longer than about 2 days.
I think every day for 3 days is more reasonable than every 5 minutes for 15 minutes, Mercedes. I'd suggest using post-1982 pennies, and cutting them into pieces./P>
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Ted Mooney, P.E. finishing.com Brick, New Jersey |
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I am doing my brother's sixth grade science fair project. Yes, he is getting away with murder because I am in 10th grade. Anyway, sodium hydroxide is a great base to test penny corrosion. It is a base with a pH level of 13 and it really surprised me. Try it. Anyone got any tips?
Andrew d [last name deleted for privacy by Editor]- Irvine, California
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Sodium hydroxide is strong and dangerous; be careful, especially to wear goggles [linked by editor to product info at Amazon]. It probably has little effect on solid copper pennies (before 1982), but I'm sure that you are right that it is murder on zinc core pennies (after 1982).
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Ted Mooney, P.E. finishing.com Brick, New Jersey |
May 13, 2009
Thank you Ted for adding some humor to this thread. :-)
I am an archaeological student and during our lunch break I found many interesting items on the beach (we're digging more inland). Of the many things I found there were about 5 handmade rusted spikes. My instructor said I could keep everything I had found there and that I should soak the items in vinegar or Coke. I threw a penny into my test bowl for fun to see it get its shine back. Just for reference sake, how long (approximately because I know there are MANY factors) would it take for the Coke to do serious damage. I'm aware that the artifacts and penny are different materials, but I was just wondering. I was also just very curious about how long it would take to corrode a penny and I also wanted to post on this thread...
- Portland, Maine
May 14, 2009
Hi, Melinda. Coke will have little effect on solid copper pennies (before 1982). It will seriously dissolve the zinc core of post-1982 pennies in a couple of days depending upon finding holes in the copper plating.
Regards,
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Ted Mooney, P.E. finishing.com Brick, New Jersey |
April 21, 2010
I am in 5th grade. I'm using pickle juice ketchup coke water and salt water to corrode pennies how long will it take and will any of them corrode?
Jordan Sstudent - Perryville, Kentucky, USA
April 22, 2010
Hi, Jordan. Make sure your pennies are 1983 or later. Ask your parents for help cutting them with tin snips to expose the zinc core. Some of them will corrode. A week is enough time.
Regards,
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Ted Mooney, P.E. finishing.com Brick, New Jersey |