The two electrodes are known as anode and cathode. Anode is the positive electrode that connected to the positive terminal of the battery; whereas cathode is the negative electrode that connected to the negative terminal of the battery. In this process, the anode must be made of plating metal; whereas cathode must be the object or metal to be plated.
Redox reaction, a chemical reaction that both oxidation and reduction occur together. Oxidation is a process of an atom losing an electron; whereas reduction is a process of atom gaining an electron. In this process, oxidation take place at anode; whereas reduction take place at cathode.
The example of half equation at anode and cathode:
Anode : Cu Cu2+ + 2e-
Cathode : Cu2+ + 2e- Cu
Furthermore, the electrolyte must be based on what the object plated. For example, to copper plate an object, the electrolyte must be in copper-based solution such as copper sulphate solution. If not, the electroplating process will be failed.
When the switch is turned on, the current is passed through the electrolyte and causes the electrolyte to splits into positive ion and negative ion. The positive ion will be attracted to cathode to gain electron; whereas the negative ions will be attracted to the anode to lose an electron. When the positive ions at the cathode gain electron, it will become atom and form a thin layer on the object.
During the electroplating process, the size of the anode decreases because of the losing of electrons, the size of cathode increases because of the gaining of electrons. Finally, to achieve a higher quality of electroplating which is attractive, resistant to corrosion and lasting, the metals need to be plated should be cleaned before the process, then a small electric current should be used, time taken for the electroplating must be longer, a dilute electrolyte should be used and the metals to be plated should be rotated slowly and consistently.
Applications of Electroplating in Daily life:
A lots of things in daily life have applied with the electroplating. For instance, the astronaut who make the First American Spacewalk in 1965 was wearing a gold plated visor to protect his eyes from solar radiation. The next example is the jewellery such as ring, necklace, bracelet and others can be plated by gold or silver to make it more attractive and valuable. The third example is that the tin cans for the food storage is plated by tin to make it resistant to corrosion and long lasting. The final example is the bath taps which plated by the chromium for protection and to make it more attractive.
Example of Electroplating (Nickel Electroplating):
The nickel electrode act as anode whereas the spoon that need to be plated act as cathode. Oxidation (lose of electrons) take place at anode; whereas reduction (gain of electron) take place at cathode. Nickel (II) sulphate solution (NiSO4) is used as the electrolyte. The nickel electrode contains of nickel atom. The spoon is made of iron which never reacts because metal atom cannot be reduced. When the switch is turned on, the current passed through NiSO4 solution and causes NiSO4 solution split into nickel ion (Ni2+), water (H2O) and sulphate ions (SO2-4). The nickel electrode (anode) lose 2 electron (oxidation) to form nickel ions (Ni2+), the 2 electrons will be transferred to the iron spoon (cathode). The Ni2+ ions from the NiSO4 solution attracted toward the iron spoon (cathode) and gain 2 electrons (reduction) to form nickel atom.
The half equation:
Nickel dissolves from the anode by releasing electrons to form Ni2+ ions. Nickel electrode becomes thinner.
Ni Ni2+ + 2e-
Ni2+ ions are discharged by accepting electrons to form nickel atom. Nickel metal is deposited on the surface of the iron spoon.
Ni2+ + 2e- Ni
Overall Redox Equation:
Ni2+ + Ni Ni + Ni2+
Next, the nickel atom will keep on forming and coat the surface of the iron spoon by forming a layer of nickel atom. When Ni2+ ions are getting used up, they will not be depleted because the present of the nickel electrode. The nickel anode become thinner because of the losing of electrons. If the nickel electrode disintegrates too much, it will replace by a new nickel. Last but not least, the thin layer of nickel deposited on the iron spoon become thicker because of the gaining of electrons. Finally, to ensure the nickel plated on the iron spoon is attractive and resistant to rusting, make sure to clean the iron spoon before plated, then small electric current is used and time taken for electroplating is longer.
Safety Precautions of Electroplating:
To prevent injured when undergoing the process of electroplating, a few safety precautions must be aware and follow. During the electroplating process, safety googles and gloves should be used to prevent skin infections. Then, the acid and cyanide solutions cannot be mixed because it will produce hydrogen cyanide gas which is a poisonous gas that is harm to our body. Moreover, cannot eat and drink during the process. Last but not least, cannot store the electrolyte in any container that made of metal because the electrolyte will react with the metal substances. Finally, the electrolyte cannot come in contact with any household cleaning materials because the reaction will releases toxic gases.