Nasser Kanani, the author of "Electroplating," describes electroplating as the process in which a metallic coating is formed from a molten salt or aqueous solution by an electrochemical reaction for the surface treatment and finishing of metals and nonmetals. Pretreatment, the deposition process and post-treatment determine the properties of surface coatings. Specifications can be met by selecting process parameters, including the deposition rate, deposition efficiency and throwing power of the electrolyte. For example, copper helps cover imperfections in base metals. High plating efficiency can be achieved, allowing coverage of parts that may be difficult to plate.
Things You'll Need
- Coin other than a penny
- Copper penny
- 1.5-volt battery
- Copper sulfate solution (100mL, 0.1M)
- Hydrochloric acid (15mL, 0.5M)
- Plastic cup
- 2 alligator clips
- Uncovered metal wires
- Paper towels
- Insulation tape
- Safety glasses
Clean the coin and the penny until they are shiny. Rinse them and dry them with a paper towel.
Wrap a wire around the copper penny. Clip the wire to the positive terminal of the battery. Wrap another wire around the coin, making sure that both of its faces are exposed, and clip it to the negative terminal. Tape over the exposed parts of the wires. Place the penny (anode) and the coin (cathode) in the cup. Tape their wires to the inside of the cup, keeping them apart.
Pour the copper sulfate solution and hydrochloric acid into the cup. Don Rathjen and Paul Doherty, the co-authors of the book "Square Wheels and Other Easy-to-Build, Hands-On Science Activities," demonstrated the effectiveness of this solution in coin electroplating. The process works as follows: Electrons from the battery positively charge the penny's copper atoms, which move into the solution. The extra electrons in the coin attract the copper ions, forming copper atoms that plate the coin.
Expose the surface of the coin previously covered by the wire and repeat the process until the coin is completely plated. Kanani argues that the surface layer may range from 5 to 25 micrometers and that the process allows uniform thickness with thin coatings, smooth surfaces, dense and fine-grained surfaces, good adhesion, high resistance to corrosion, good ductility, reduced internal stress, high strength and hardness, good wear resistance and low and uniform coefficient of friction.
Tips & Warnings
- Use safety glasses as a precaution.
- "Electroplating;" Nasser Kanani; 2004
- "Square Wheels and Other Easy-to-Build, Hands-On Science Activities;" Don Rathjen and Paul Doherty; 2002
- Photo Credit Stockbyte/Stockbyte/Getty Images