Why Do Pennies Turn Brown

Many of you often wonder that why pennies turn brown. In view of many people, pennies get this brownish color because of rust. This viewpoint is just about enough to understand the brown color of pennies. We can associate the rust formation on iron with the fact why pennies turn brown.

Properties of Copper

Pennies are normally made of copper alloy and this again cause many of you to think why copper is preferred for minting coins. Perhaps, the answer to this question is based on the properties of copper as to why it is chosen to mint coins. Having a good knowledge about the properties of copper will give us the answer of our question.

Pennies Turn Brown  Why Do Pennies Turn Brown

Looking Into Copper Oxidation

We all know that iron becomes rusty when it is exposed to water or open air and this process of rust formation is known as oxidation. In simple words, oxidation is a process wherein oxygen becomes in contact with compound. This reaction takes place because of two reasons, i.e. loss of electrons and reduction. Other than iron, this process also takes place in other things also.

We can explain this with a simple example. Simply cut an apple in half and expose its inner surface to air for a while and you will notice that the flesh of an apple begins to turn brown after some time. This happens because of oxidation. We have given this example to make you understand that why and how pennies turn brown. But you have to be clear here that the oxidation process for pennies is far different than the oxidation process for apple or iron.

A Non-Corrosive Oxidation

As pennies are made of copper alloy, so the major difference you notice between the iron and pennies is that pennies don’t corrode. Copper is a chemical element that doesn’t produce any tarnish and also doesn’t emit anything as iron or some other metals do. What actually happens, the oxidized copper turns green in color and a layer called patina cover the surface of copper. Patina is a kind of coating comprises of different compounds that offers protection to copper rather than corrode it.

Why Pennies Turn Brown and Not Green

Now you may be thinking that if oxidized copper turns green then why pennies turn brown. What actually happens in case of copper, the brown tarnish appears on pennies is basically a combination of oxidation of copper and copper’s intrinsic quality of drawing minerals.

In simple layman’s words, apart from oxidizing, copper also has the ability to attract other minerals present in the dirt or other things around. When people treat coins in different ways this process leads then to turn brown in the long run. It is not a matter of day or two as copper pennies take their time to turn to brown color.

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