Applications of Electrolysis

What is Electroplating?

Electroplating is a controlled electrolysis process where the surface of one metal is coated with a thin layer of a different metal. Think of it as using electricity to spray a protective or decorative metallic coat onto an object.

Real-world examples:

• Coating iron tools with nickel to prevent rust
• Coating steel car parts with chromium for a shiny, corrosion-resistant finish
• Plating cheap jewellery with gold or silver to make it look expensive and resist tarnishing
• Coating steel with zinc (galvanising) — the zinc sacrificially corrodes instead of the steel underneath

The Setup: Three Essential Parts

Every electroplating cell has three crucial components. Understanding which is which is absolutely essential for exam success.

1. The Cathode (−) — The Object to be Electroplated

This is the negative electrode. The object you want to coat goes here. If you're electroplating a steel fork with silver, the fork is the cathode. Metal ions from the solution will migrate toward the cathode and be reduced (gain electrons), depositing a shiny layer of metal onto it.

2. The Anode (+) — Pure Metal to be Applied

This is the positive electrode, and it is made from the pure metal that you want to plate onto the object. If you want to plate with silver, the anode is pure silver. As current flows, atoms of the anode lose electrons and dissolve into the solution as ions, maintaining a constant supply of metal for the cathode.

3. The Electrolyte — Dissolved Metal Salt

This is an aqueous (water-based) solution containing a soluble salt of the pure metal at the anode. For example:

• To plate with silver: use a solution of silver nitrate (AgNO₃) or silver sulphate
• To plate with tin: use tin(II) chloride (SnCl₂)
• To plate with copper: use copper(II) sulphate (CuSO₄)

The electrolyte ensures there are enough metal ions available to be deposited.