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Q&As since 1989


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What Makes a Penny Rust?

2001

HI.

MY DAUGHTER IS DOING A SCIENCE FAIR PROJECT! IT IS ON WHAT CHEMICALS WILL MAKE THE PENNIES RUST?

CAN YOU HELP US - THANKS.

Peggy L. [last name deleted for privacy by Editor]
- West Babylon, New York

The fact is a penny will not rust to the point that it isn't copper. It is made of zinc and some other non-corrosive metal and only under extreme conditions will it even begin to mildew let alone rust. I hope my answer helps.

Jango F. [last name deleted for privacy by Editor]
- Hampton, Virginia
2003

The penny will not rust but if you want to see something cool where you get a good mark put a penny into a Coke can and another one in a Sprite can. Leave it like that for a few days and see what happens. Last year I got 91% on this project.

John S. [last name deleted for privacy by Editor]
- New York, US
2006

Pennies rust with coffee or with clorox. Leave the penny in one of these liquids for 20 to 40 minutes and when you take it out it will be rusty.

Alison R. [last name deleted for privacy by Editor]
- Bronx, N.Y.
May 12, 2008

Hi, Alison. Thanks for the tip on how to make pennies corrode. Actually, the word "rust" is not quire correct, though, because rust is defined as iron oxide, and there is no significant iron in pennies, bleach, or coffee -- so no matter how extensively the penny corrodes, it can never "rust". Much like you can leave a dead fish out in the sun and it can become quite rank, but it can't ever become a rotting cabbage :-)

Readers who are attempting this should know that pennies minted before 1982 were solid copper, and pennies minted after 1982 are zinc with a thin plating of copper over it. They behave differently.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 12, 2008