How long does it take for a penny to rust? Technically, the penny doesn’t rust, the copper plating on its surface only corrodes which results in a green surface tarnish. The corrosion occurs due to the chemical reaction that occurs between the metal, moisture or water, oxygen, and CO2 (carbon dioxide) in the air.
The common green color known as ‘green patina’ seen on old pennies can take up to twenty years to form if it is not dipped in an extra solution. Because a penny cannot rust, this article has explained corrosion on a penny, why and what makes a penny to corrode, how to tarnish a penny yourself, what can fasten the process, and how to clean a penny that has undergone corrosion.
Why Does A Penny Corrode?
Looking at a penny, you will see that it looks like copper, but it’s a combination of a few metals like tin, steel, copper, zinc, or nickel unless it’s an old piece of a penny. Even if a penny has a mixture of these other metals, the outer coating is almost always copper, and exposing it to the atmosphere will make it corrode.
The pennies that contain a high amount of zinc will not corrode because of their high resistance to atmospheric corrosion.
Why Pennies Change Color?
Pennies change color due to corrosion. Copper, which is a significant component of a penny, tends to corrode when exposed to sulfur or oxygen, even though it has a high level of resistance.
This means that even the oxygen we breathe in every day can corrode a penny when the oxygen molecules react with the copper in a chemical process called oxidation. After the oxidation reaction, a layer of green film will be seen on the surface of the penny signifying that corrosion has taken place.
This green film deposited on the surface of the penny is sometimes known as patina and its scientific name is known as ‘copper hydroxide carbonate.’
How to Clean Corroded Pennies?
Cleaning dull or corroded pennies isn’t difficult. Simply dip them into a solution of salt, water, and vinegar. While the acetic acid in the vinegar dissolves copper oxides, the salt will speed up the rate of the reaction.
You can also use lemon juice that contains citric acid to clean corroded pennies, and cleaned corroded pennies normally turn bright again within a few seconds.
How to Tarnish a Penny
If you want to tarnish a penny, a simple exposure to oxygen, moisture, and carbon dioxide will do the trick, or you can apply ordinary household items to it which will catalyze to increase the rate of the chemical reaction.
What Will Tarnish a Penny Faster?
Over time, the color on the surface of some pennies starts to disappear. If you have seen a brand new penny, you will notice that something changes on the penny with time. If you put the new shiny one close to a pack of some dull and old ones, you will see that the tarnished color of the older ones will be seen.
Like in metals, the tarnishing on pennies occurs as a result of the oxidation process, or the reaction between oxygen and sulfides with the surface of the penny.
Here are some liquids that can act on a penny making it tarnish faster:
The rate of the oxidation process that occurs on copper can be increased by acids. When you dip a penny inside a little quantity of vinegar, it will initiate a reaction that will start to tarnish the penny. Also, vinegar as the acid can easily dissolve the zinc core of a penny but cannot dissolve copper.
Bleach is an alkaline chemical that can dissolve the zinc present in the core of a penny, and contains a high level of chlorides, which are also destructive to the rusting process of most metals. Leaving a penny in a bleach solution for some time will make the penny start to darken and eventually turn green.
Introducing bleach to copper will speed up the process through which it gets those green spots and darkened tarnish, artificially. If you check many old pennies, you will see some combination of green spots and the darkening of the original shiny and bright copper color, all that can be made possible by the addition of bleach to the surface of a penny.
3. Potassium sulfide
When potassium sulfide is dissolved in water, it gives a solution that is capable of tarnishing a penny. The ratio of water to potassium sulfide to be used to make the solution is 5:1; for every 5 drops or addition of water, use one drop of potassium sulfide.
When the penny is introduced into the solution for a very short time, the tarnishing process starts, but a continuous drying and re-dipping of the penny several times in the solution will give the penny a natural tarnish look.
Frequently Asked Question (FAQ’s)
Can Rusting Occur in a Coin?
No, a coin is not an iron or steel, so it cannot rust because rust is an oxide of iron and an outcome of the corrosion process of steel or iron.
Can Rusting Occur in a Dime?
No, a dime cannot rust because it is neither steel nor iron, but it can tarnish or corrode. The process of tarnishing or corrosion in a dime can take a minimum of two weeks to complete.
A penny doesn’t rust due to the presence of copper and other metal components. Copper resists the formation of oxides but forms a greenish coating on the surface of the penny when exposed to oxygen in the atmosphere.
This green coating film known as patina takes years to form unless some household items like bleach, salt, and vinegar are used to speed up the tarnishing process.