How to electroplate copper

Warning: Copper sulfate is poisonous if swallowed, and the blue color makes it very attractive to small children. Do not leave the crystals or solutions unattended around very young children, who may try to eat or drink them! 

Description: Dissolved copper can be plated onto a metal surface using electricity. Learn how electroplating works.

Equipment needed:

Copper Sulfate. This is one of the most soluble copper compounds, it makes bright blue crystals and dissolves fairly easily in water. You can buy it in hardware stores in several forms, the form I found was Roebic Root Killer (used to clear roots out of sewers and septic systems).

Click the photo to view the larger-sized picture.

A small DC power supply.  A “wall-wart” power adaptor like this one works fine.  I expect that pretty much everyone has at least one or two of these around, orphaned when the electronic gadget that it went with broke down. This power supply came from . . . from . . . well, to tell you the truth, I don’t know what it came from.  All I know is that, whatever it was supposed to provide power to, we don’t have it anymore.

A couple of “alligator clips“, to put onto the wires from the power adaptor. These cost about 50 cents each at the hardware store.

Wire stripper (optional, if you’re handy with scissors)

A screwdriver, that matches the type of screws on your alligator clips.

A small plastic or glass container (something small and disposable, like a small jelly jar or a yogurt cup, is good)

A chunk of copper that will fit easily into your container, and that is thin enough to clip on an alligator clip, and long enough to stick out of the container (a piece of heavy copper wire, or a copper sheet, are both good.  You can get these at any hardware store).  This will be one electrode of your electroplating cell.

A large steel nail that is long enough to stick out of the container.  This will be your second electrode. 

A plastic or wooden stirrer for mixing the solution (a coffee stirrer or a wooden skewer are both good.  Don’t use a metal spoon to stir it, because it will plate copper onto the metal)

A multimeter, either a digital multimeter or an analog multimeter. (It’s optional, you can do the experiment without this, although it does help.)

The Digital Bits Science Lab Experiment:

First, prepare your power supply.  Cut off the end that would normally plug into the piece of electronics, and pull the two strands of wire apart. 

Strip the insulation off of the ends, and put on the alligator clips so that your power supply looks like this:

Put a spoonful of copper sulfate into the container, add water, and stir until the copper sulfate dissolves.

Put in the piece of copper and the nail, with the ends sticking up:

Now, if you have a multimeter, you can check the polarity of your power supply.  Clip the red (+) lead of your multimeter into one of the alligator clips, and the other (-) lead into the other clip.  Set your multimeter to read DC volts, and plug in the power supply.  If you get a positive reading, then you know that the power supply lead connected to your red multimeter lead is the positive lead. If you get a negative reading, swap the power supply leads and try again.

OK, now clip the POSITIVE lead of the power supply to your copper electrode, and the NEGATIVE lead to the steel nail.

If you don’t have a multimeter, just guess which one is which, we’ll be able to figure it out once we turn it on.

Carefully check to make sure that the two electrodes are not touching each other, ideally keep them about an inch apart.

And now, plug in the power supply and watch what happens over a period of about 10 minutes or so.

If the polarity is correct, then you will get metallic copper plating onto the nail, with maybe a small amount of bubbles forming on the nail as well.  Meanwhile your copper electrode will tarnish and turn dark brown or black.  If you leave it running for half an hour or so, you should get a deposit of copper something like this on the nail:

If you have the polarity backwards, then your nail will bubble vigorously, and while there may be a thin film of copper on the surface, it will never build up a significant thickness of copper. 

What’s happening here?

This is an electrolysis reaction.  What we are doing is pumping electrons into one electrode (the nail), while pulling electrons out of the other electrode (the copper).  When you add electrons to a copper sulfate solution, the copper sulfate turns to metallic copper and sulfuric acid. The metallic copper is not soluble in water, so it plates out on the electrode where we are adding electrons.

Meanwhile, at the other electrode we are pulling out electrons.  This makes the metallic copper there react with the sulfuric acid in the solution to make more copper sulfate. 
The overall effect is that copper dissolves from the copper electrode, travels over to the iron electrode, and plates out there as metallic copper.

By adding “smoothing agents” to the solution, it is possible to make the copper plate out as a smooth, shiny metal coating. Similar things can be done with other metals, like gold, silver, zinc, chromium, and nickel.  The metal coatings can be decorative, or they can protect the metal underneath from being corroded, or both.

Other articles related to this topic:

• How to make copper metal from dissolved copper compounds
• Multimeter experiment with voltage and current
• Multimeter experiments and introduction
• Multimeter experiments with electricity and water
• Easy electrolysis - how to make your own hydrogen