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topic 7854

What Will Make a Penny Rust?


(2001)

Q. I want to find out what makes a penny rust?

We are using 5 new pennies and putting them into 5 different things. We have gasoline, soda (coke), glass clearer, fish tank with salt, ammonia with salt in it . My daughter wants to find out which will make a penny rust. She is only 11 years old.

Thanks so much!

Peggy L [last name deleted for privacy by Editor]
- New York


(2001)

A. Hello Peggy.

Stop! 11-year-olds should not be using gasoline in such experiments! She could try 3-in-1 oil or sewing machine oil or motor oil as a petroleum-based entry in her tests.

And I would also advise her not to mix other ingredients into household cleaners; while I don't really think that salt is dangerous to add to ammonia, in principal it is dangerous to add things to ammonia or bleach, or to household cleaners containing either.

She could try beer, rubbing alcohol, vinegar, lemon juice, vegetable oil, antifreeze, or shampoo for additional ideas.

Nothing will make a penny rust because rust is "iron oxide", so only things with iron in them can "rust", whereas a penny is made of copper plated onto a zinc core. But anything acidic or salty will cause the pennies to corrode. If you can bend, saw, or cut the pennies so the silvery colored zinc core is exposed, they will corrode much quicker. Good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


April 19, 2012

Q. I just want to know can orange juice, soda (cola), and water make a penny rust?!

I need this answer for my science fair project ASAP, and for my grandmother she wants to know and so do I.

This will mean a lot Thanks!

Kristien B [last name deleted for privacy by Editor]
kristy forever - cleveland,ohio,united states


April 19, 2012

A. Hi Kristien.

What part of "Nothing will make a penny rust because rust is "iron oxide", so only things with iron in them can "rust", whereas a penny is made of copper plated onto a zinc core" didn't you understand? :-)

Remember rust is iron oxide, a reaction between iron and oxygen. If you don't have iron, you can't make rust. Pennies have no iron in them. They can "corrode" or "tarnish" or "discolor" though. Good luck!

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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