Electroplating
Electroplating is a common industrial process. By applying an electric current, a layer of metal such as copper or nickel can be deposited onto a conductive object. In this experiment, a 9-V battery is used as the energy source to drive the electroplating process. A copper plate and a graphite rod are used as the cathode and anode in the process, respectively.
Nickel ion solution is used as the electrolyte. Under the influence of the battery, positively charged nickel ion can migrate to the cathode, pick up electrons and deposit on the surface of copper electrode. To create a special feature onto the metal surface, prior to the electroplating process, the students can draw a picture on the copper plate with an oil-based marker. Since the ingredients of the marker ink do not conduct electricity,
Nnickel ions will not deposit on the trail of the drawing. After removing the ink pattern by acetone, an electrically plated product with artistic input from the students can be produced.
To make the activity more educational, a simple treatment method for the metal plating solution will be introduced. Metal ions in industrial waste water must be removed first before its discharge. This can be achieved by mixing the waste water with coagulant and flocculant. A coagulant is a substance that causes a liquid to coagulate to form solid or semi-solid materials, while a flocculant is a substance which promotes the clumping of particles. Both the coagulant and the flocculant react with the wastewater to form settleable-sized flocs, which are allowed to settle and collected as sludge at the bottom of the container.
Conducting the electroplating experiment
1. Clean the surface of a copper plate with sand paper to remove metal oxide.
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2. Draw a picture according to the student’s own design on the copper plate with an oil based marker.
3. Connect the copper plate (used as the cathode) to the negative pole of a 9-V battery and a graphite rod (as the anode) to the positive pole of the battery. The electrical circuit is set up in the manner as shown in the diagram below.
| Connecting the electrodes with a 9V battery | Electric circuit diagram |
4. Dilute 20 ml of concentrated nickel plating solution* with de-ionized water to make up to 300 ml of plating solution.
*Prepared by dissolving 2 g NiCl2.6H2O in 500 ml of 0.12 M HCl.
5. Put two electrodes into the solution and connect the circuit with a 9 V battery.
6. Allow the process to run for 10 to 15 min, disconnect the 9-V battery, take out the copperplate and rinse it with sufficient amount of water.
7. Use acetone to remove the marking trail to furnish the end product.
View Comments
am willing to have such experiment on my own.
I wish I could do this expt with my students BUT nickel salts are prohibited from use by kids -- they are carcinogenic