Here is an experiment on ‘Electroplating Plants’ especially written for school and college students.
Aim of the Experiment:
Study on electroplating by visiting an industry.
Objective:
Electroplating of copper on a copper plate
Apparatus Required:
A glass plating tank with plastic lid, voltmeter, ammeter, copper plates, rheostat, one way key, piece of sand paper, cleaning and pickling baths, copper sulphate and sulphuric acid.
Theory:
ADVERTISEMENTS:
Electroplating is a process of providing metallic coatings by means of electrolysis. If the article to be coated is metallic, then the base metal and the coated metal may be same. Some common metals and alloys, of which coating can be provided on metallic surfaces include chromium copper nickel, silver, gold, etc.
The main elements involved in this process are an electrolyte, a tank and electrodes and dc source of low voltage. The object to be plated are suspended and immersed in the electrolyte filled in the tank. Electrically they are connected to the negative terminal so as to act as a cathode in the circuit. The material to be deposited to provide coating is connected to the positive terminal, so as to act as anode.
Preparation of Electrolyte:
Clean the empty glass plating tank to remove dust and other solid particles. If any grease or oil still lying in it, then remove it with kerosene or Na2 CO3 solution. After rinsing with water, wash with acid pickle. Again rinse many times with fresh water and in the last with distilled water.
ADVERTISEMENTS:
Now fill the tank about two-third with distilled water, add the require amount of copper sulphate and dissolve with the help of stirrer. Now add required quantity of sulphuric acid and with constant stirring.
Preparation of the Electrodes:
Copper plates should be cleaned by dipping them in NaOH solution followed by rinsing in hot water. Wash in running tap water and then agitate each plate for 15 to 30 seconds in acid pickle.
Procedure:
ADVERTISEMENTS:
1. Draw the circuit as shown in figure 21.
2. Clean the ends of the connecting wires with sand paper.
3. Remove the plug from key ‘k’ and connect the battery, the rheostat, the electrolytic both along with two copper plates.
ADVERTISEMENTS:
4. Connect the voltmeter in parallel with supply and ammeter in series.
5. Put the stirrer for agitation of plating solution.
6. Now put the object to be electroplated in the centre of two plates and connect the negative terminal of battery.
7. Find the area of both sides of object dipping into electrolyte.
ADVERTISEMENTS:
8. Put the plug into key.
9. Note down the reading of ammeter at 5-minute intervals and see that it remains constant.
10. If necessary, adjust the current by manipulating the rheostat.
11. After half an hour, remove the plug from key and take out the object to be electroplated.
12. Rinse the object immediately in dilute sulphuric acid.
13. Then wash it thoroughly in running tap water, rinse in distilled water and dry.
Observations and Calculations:
(i) Area of the both side of the cathode dipping in the electrolyte = x cm2
(ii) Current required for good deposit = 0.02 x – 0.1 x – A
Precautions:
1. The object to be electroplated must be cleaned thoroughly.
2. All connections must be clean, tight and free of corrosion.
3. The object to be electroplated must be connected to negative terminal of supply.
4. The electrodes should not be touching each other.
5. The current supplied by battery during the process should be constant.
6. The plate must be rinsed in dilute H2SO4 soon after removing from electrolyte, otherwise the deposit will turn back.