How does pennies rust

Phil Newton answered. How do pennies corrode? How to reverse the process? Here's how to do it: Simply fill a container with water, salt, and vinegar. Place the coin in the mixture and wait for a few minutes.

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April 10, Joe Ford. Table of Contents. I am doing a science fair on which metal takes longest to rust in tap water. I have zinc, copper, silver, aluminum, and a galvanized metal. I really need to know, which metal rusts fastest, copper or silver? We put your question onto a page that mostly already answers it, Lenny. But to repeat, a cod can rot and a cabbage can rot. But if you ask "which becomes a rotting fish faster if you leave it in the sun? Similarly, rust is iron oxide, sort of "rotted" iron; copper and silver can never become rotted iron because they are not iron.

So your question might actually be which corrodes faster or which tarnishes faster. Now, which tarnishes faster is something your science fair project will determine.

But neither will corrode a lot; after all, the copper piping in your house and your mom's silver service wouldn't be very useful if they quickly corroded away. I would like to thank you I read each of your responses and they helped me a lot! Thanks so much for the kind words, Maria. You made my day. But YOU did the project, so be proud of your effort.

Regards, Ted Mooney , P. Striving to live Aloha finishing. Pennies do not rust. The stuff that gets on them is a form of corrosion. Corrosion is, when on copper, brown-ish mold begins to form. The word for this mold is Patina.

I hope this helps you! Best of luck The composition of pennies changed in late , when zinc became the primary metal instead of copper. Before , pennies were forged of 95 percent copper and 5 percent zinc. However, as copper became more expensive, it was abandoned as the primary metal. Pennies are now made of a zinc core and a thin copper coating. Coins made of zinc can cause a corrosive reaction when they are exposed to gastric acid.

O'Hara and associates conducted a study to determine the radiographic appearance and features of corrosion in coins exposed to gastric acid. The authors became interested in the effects of corrosion of a coin in the stomach when they encountered a two-year-old boy who presented to the emergency department with abdominal pain and vomiting four days after he had swallowed a coin.

Initial radiographs of the child showed an intact metallic disk, which was presumed to be a coin, in the stomach. However, radiographs four days later showed a metallic object with a moth-eaten appearance. Endoscopy yielded a blackened, corroded penny and revealed a bleeding gastric ulcer. The authors analyzed corrosion after exposure to hydrochloric acid in four types of coins: three silver-colored coins a quarter, a nickel and a dime , six pre pennies that were worn but not intentionally damaged, six post pennies in good condition and six post pennies that had been scratched by scraping the edges until the zinc was exposed.

Each group of coins was immersed in hydrochloric acid in a concentration that approximated gastric acid. The coins were rinsed and radiographed daily for seven days. Each group of coins was weighed at the beginning and at the end of the study. In addition, the penny retrieved from the two-year-old patient was weighed.

Immersion of the damaged post pennies in the hydrochloric acid was immediately followed by the development of bubbles of gas, indicating an immediate chemical reaction. With the undamaged post pennies, bubbles were seen on the surface by the third day of immersion in hydrochloric acid. Bubbles were not seen at any time on the silver-colored coins or the pre pennies.

The surfaces of all of the coins grew increasingly dull as the duration of exposure to hydrochloric acid increased. Radiolucent erosions were radiographically visible on the post pennies within 24 hours of immersion in the hydrochloric acid. Keep the penny in the cup. In each case, make sure the penny is completely covered by the contents of the cup. This is your control.

Complete the full procedure. Keep your gloves on for this part, being careful to keep each penny with its labeled cup. Scrub each penny for 10 seconds, then rinse it again with water and place it back into its cup. Set these cups aside for now. Start a timer for five minutes. Once all the pennies are in their correct cups, use the remaining time to observe the pennies and the contents of the cups. Do you notice any changes in the appearance of the pennies? What is changing? Do you notice any changes in the contents of the cups?

Is anything bubbling or changing color? Once five minutes have passed, rinse the cups with water until their insides and the pennies are clean. Be careful not to lose your pennies. Keep the pennies in the cups.

Once all of the pennies have been rinsed, use your fingers to gently scrub the pennies one at a time with your baking soda paste.

Again, keep your gloves on for this part. Go back to the table you drew. Use your paper towels to gently dry off each penny then place it in the corresponding square of your table.

How does time affect the cleanliness of the pennies? Was one or five minutes more effective in cleaning the pennies overall? Can you think of why time would be important? Were there any cleaning methods where the time didn't matter, so the "1 Minute" and "5 Minutes" pennies are equally clean?