What will make a penny rust?

Letter 7854

What will make a penny rust?

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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 LaSala
- New York

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Hello Ms. LaSala

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

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

Nothing will make a penny rust because only things with iron in them can "rust", whereas a penny is made of copper plated onto zinc. 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 is exposed they will corrode much quicker.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

Ed. note: Sorry, but for every metal finisher in the world there are a thousand students, and we are drowning under variations on this question which we've answered hundreds of times already. It's time for the students to read our F.A.Q. on the subject rather than to keep asking us to answer the question for them individually

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