Electroplating: Copper-Plated Key

Electroplating uses a form of electrolysis in which the electrodes play a bigger role than just conducting the current.

Using electricity, you can coat the metal of one electrode with the metal of the other in an electroplating process, also known as electrochemistry.

Electroplating, also known as electrodeposition, is essentially a chemical reaction that helps to make various items we see and use every day. There are also specific types of electroplating such as copper plating, silver plating, and chromium plating. Jewelry and silverware can be silver- or gold-plated, while zinc is often used to coat iron to protect against corrosion. Professional electroplating requires specialized chemicals and equipment to make a high-quality coat, but in this project, you can try your hand at a simple procedure that will transfer copper (a versatile, naturally occurring metal) to a brass key.

Being red in color, copper is known for its high electrical conductivity, malleability, and corrosion resistance. In copper electroplating, a metal substrate is placed in an electrolytic bath and an electric current is used to cause copper ions to adhere to the base material's surface.

(Adult supervision and chemical safety equipment required.)

Watch us use electricity to copper-plate a brass key (copper electroplating) in this Home Science Tools video. See this project in action!

What You Need:

1.5-volt D battery with the battery holder (for power supply)
Two alligator clip leads or insulated wire
Beaker or glass (250-ml beaker is recommended or similar glass size)
Copper strip (pure copper)
Copper sulfate
Copper electrode (or coil of copper wire)
Brass key
Safety equipment

How to Electroplate Copper:

Prepare the key for the DIY copper plating by cleaning it with a thin layer of toothpaste or soap and water. Dry it off on a paper towel.
Stir copper sulfate into some hot water in a beaker until no more will dissolve. Your solution should be dark blue. Let it cool.
Use one alligator clip and attach the copper electrode to the positive terminal of the battery (this is now the anode) and then attach the key to the negative terminal (now called the cathode).
Partially suspend the key in the solution by wrapping the wire lead loosely around a pencil and place the pencil across the mouth of the beaker. The alligator clip should not touch the solution.
Place the copper strip/mass of copper into the solution, making sure it doesn't touch the key. The plating solution level is now below the alligator clip. The copper strip will produce a path for conductivity. An electrical circuit has now formed with the positive electrodes & negative electrodes and an electrical current is flowing.
Leave the circuit running for 20-30 minutes, or until you are happy with the amount of copper on the key.

What Happened During the Plating Process:

The copper sulfate solution is an electrolyte solution that conducts electricity from one electrode to the other, creating an electrical current.

When the current is flowing, oxidation (loss of electrons) happens at the copper anode, adding copper ions to the solution.

Those ions travel on the electric current to the cathode, where reduction (gain of electrons) happens, plating the copper ions onto the key.

There were already copper ions present in the copper sulfate solution before you started, but the oxidation reaction at the anode kept replacing them in the solution as they were plated with a thin layer onto the key, keeping the reaction going.

This project has many variables, including the cleanness and smoothness of the key, the strength of the copper sulfate solution, and the strength of the current.

If a black soot-like substance starts forming on the key, your solution is not strong enough for the current. Take the electrodes out and add more copper sulfate. When you put them back in, make sure the anode and cathode are as far apart as possible. Be sure to take notes for your science experiment to ensure you have great data collection.

There are lots of projects you can do with electroplating!

One fun idea is to use a flat piece of brass as your cathode and draw a design on it with an oil-based marker. The copper will not bond where the marker is.

After you're done plating it, you can use acetone (or nail polish remover) to wipe off the marker, leaving a design of the brass showing through the copper. Copper is relatively dull in color, which means other additives may be needed if a brighter finish is required. You can use a little metal polish to make the copper shiny if you desire.

You may want to try this simple copper-plating experiment that doesn't use electrolysis and requires only household materials.