HL Extension
Industrial Electroplating Principles
Electroplating uses electrolysis to deposit a thin, protective or decorative layer of a metal onto an object acting as the cathode in an electrolytic bath.
Electroplating Setup
| Component | What to Use | Why |
|---|---|---|
| Cathode (-) | Object to be plated | Metal ions are reduced onto its surface |
| Anode (+) | Pure plating metal | Dissolves to replenish metal ions in solution |
| Electrolyte | Solution of plating metal salt | Provides the metal ions (e.g., CuSO₄ for copper plating) |
Applications of Electrolysis
| Application | Details |
|---|---|
| Electroplating | Chromium/nickel plating of cutlery, taps, jewellery |
| Aluminium extraction | Hall-Heroult process: electrolysis of Al₂O₃ in molten cryolite |
| Chlor-alkali industry | Electrolysis of brine producing Cl₂, H₂, and NaOH |
| Copper purification | Impure Cu anode dissolves; pure Cu deposited at cathode |
Exam Tip
Summary: Electroplating Cell Setup
- Cathode (−): Object to be plated (receives metal coating: \(\text{M}^{n+} + n\text{e}^- \rightarrow \text{M(s)}\)).
- Anode (+): Pure coating metal (dissolves to replenish ions: \(\text{M(s)} \rightarrow \text{M}^{n+} + n\text{e}^-\)).
- Electrolyte: Solution of soluble salt of coating metal.
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