Electroplating

Electroplating

• is forming a thin layer of one metal on the surface of another to give it a shiny attractive appearance or to protect it from corrosion.
• Car fittings made of steel are chromium-plated; taps and mixers are plated with chromium or gold; cheap metals are given the value and look of silver or gold.

To silver-plate a (copper) spoon or jug:

1. Clean the object thoroughly (remove grease and oxide).
2. Dip it in a solution containing silver ions (e.g. silver nitrate).
3. Place a bar of pure silver in the same solution.
4. Connect the object to the negative pole of a d.c. source (it becomes the cathode) and the silver bar to the positive pole (the anode).

• Anode: Ag(s) → Ag⁺(aq) + e⁻ (the silver bar dissolves)
• Cathode: Ag⁺(aq) + e⁻ → Ag(s) (silver deposits on the object) The concentration of Ag⁺ in the bath therefore stays constant. The thickness of the layer depends on current and time (Faraday's laws).