Copper Plating a Key as a Science Project

The techniques used to plate copper are also used to refine copper.

Electroplating copper onto a key essentially involves immersing the key and a strip of copper into a plating solution that contains dissolved, charged copper atoms. A DC power source then supplies an electric current that migrates from the key, through the solution, to the copper strip. In the process, the charged copper atoms convert to metallic copper atoms as they "plate" from the solution onto the key.

Things You'll Need

• 1 gallon distilled water
• 3 500-mL Erlenmeyer flasks
• Ice
• Large plastic bowl
• 40 mL concentrated sulfuric acid
• Balance or scale capable of measuring to 1 g
• 30 g sodium hydroxide pellets
• Copper strip, 1 cm x 10 cm
• Steel wool
• Tweezers
• Paper towels
• 250-mL beaker
• 10 cm of uninsulated 20-gauge copper wire
• DC variable power supply
• Ammeter
• 1-foot insulated wires with alligator clips, 3

Instructions

Preparation of Solutions

1. Prepare a 3 M sulfuric acid solution by adding about 200 mL of distilled water to a 500-mL flask and chilling the flask on an ice bath in a large plastic bowl. Measure 40 mL of concentrated sulfuric acid in a 100-mL graduated cylinder and slowly add it to the chilled water. Allow the solution to cool--it will become hot as the acid is added--and add distilled water to a total volume of 250 mL.

2. Prepare a 3 M sodium hydroxide solution by weighing out 30 g of solid sodium hydroxide pellets on a balance and adding them to 200 mL of distilled water in a 500-mL Erlenmeyer flask. Swirl until the solid has dissolved. After the solution has cooled, add distilled water to a final volume of 250 mL.

3. Prepare the plating solution by weighing out 50 g of copper sulfate pentahydrate and dissolving it in 100 mL of distilled water in a 500-mL Erlenmeyer flask. Add 10 mL of 3 M sulfuric acid solution prepared in step 1. Swirl the mixture and add distilled water to a final volume of 200 mL.

Electroplating

1. Scrub the key and copper strip with steel wool, then wash the key and electrode under running tap water. Immerse both the key and a 1 cm x 10 cm copper strip in about 30 mL of 3 M sodium hydroxide solution for a few minutes. Remove the key and strip with tweezers and rinse them with distilled water, then immerse them in 30 mL of 3 M sulfuric acid for a few minutes. Remove them with tweezers, rinse them with distilled water and blot dry with a paper towel.

2. Bend one end of the copper strip and hang it over the inside edge of a 250-mL beaker. Wrap a 10-cm piece of 20-gauge copper wire around a glass rod and suspend the key from one end of the wire. Place the glass rod across the top of the 250-mL beaker containing the copper strip such that the key "hangs" inside the beaker. Make certain the copper strip and key do not contact each other.

3. Connect the negative terminal of the DC power supply to the copper wire from which the key is suspended. Connect the positive terminal of the power supply to one terminal of the ammeter. Finally, connect the other terminal of the ammeter to the copper strip.

4. Add the plating solution to the beaker so that the key is completely submerged. Then turn on the power supply and adjust the current until the ammeter reads 0.25 amps. Allow the current to flow for 30 minutes. Adjust the power supply as necessary during this period to maintain a 0.25-amp current.

5. Turn off the power supply and remove the key from the solution. Rinse the key with distilled water and blot dry with a paper towel. The key should exhibit a uniform copper coating.

Tips & Warnings

• Some keys work better for this procedure than others. Nickel-plated keys tend to work best, but be prepared to experiment with various keys to achieve optimum results.

• Concentrated sulfuric acid and sodium hydroxide pellets are corrosive to skin. The use of safety goggles and latex gloves is highly recommended.

References

• Case Western Reserve University: Electrochemistry Encyclopedia: Electroplating
• American Institute of Physics: The Discovery of the Electron
• University of Nebraska-Lincoln: How to Copper Plate Your Car Keys

Resources

• University of Wisconsin-Madison: Refining of Copper