Reactivity 3.2.16 — Electroplating

 Electroplating is the process of depositing a thin layer of metal onto the surface of another material using electrolysis. It is widely used in industry to enhance appearance, prevent corrosion, reduce friction, or improve wear resistance.

Components:

• Cathode: The object to be plated (connected to the negative terminal)
• Anode: A rod of the metal to be plated (connected to the positive terminal) or an inert electrode
• Electrolyte: A solution containing ions of the plating metal (e.g., CuSO₄ for copper plating)

Basic Principle: Metal cations in the solution are reduced and deposited onto the cathode. If a metal anode is used, it dissolves into the solution to maintain the ion concentration.

 Copper Electroplating

Setup: Cathode = iron spoon, Anode = copper rod, Electrolyte = aqueous \( \text{CuSO}_4 \)

Electrode Reactions:

Cathode (Reduction):

\( \text{Cu}^{2+}(aq) + 2e^- \rightarrow \text{Cu}(s) \)

Anode (Oxidation):

\( \text{Cu}(s) \rightarrow \text{Cu}^{2+}(aq) + 2e^- \)

Net Effect: Copper metal from the anode dissolves and is redeposited on the cathode surface.

Key Points:

• The mass of metal deposited is proportional to the quantity of electricity passed (Faraday’s Laws).
• The electrolyte must contain ions of the metal to be deposited.
• The object being plated must be clean and conductive.

Common Electroplating Metals:

• Copper (for electrical conductivity and aesthetics)
• Silver (for jewelry and tableware)
• Chromium (for corrosion resistance and shine)
• Nickel (for wear resistance and base layer)

Factors Affecting Electroplating:

• Current density (controls rate of deposition)
• Temperature (affects ion mobility and coating quality)
• Electrolyte concentration