Plating is a surface is covered with a thin layer of metal, being usually a conductive surface. This has been used for hundreds of years and is still used nowadays. It is used for decorating objects, for corrosion inhibition to reduce friction or improve weareability and for other industrial purposes. Plating is also used for jewelry finishing.
Electroplating is the main method used for plating. The process consists in moving the metal ions from a solution by an electric field to coat an electrode, using electrical current. The process uses a cathode (the part to be plated) and an anode (the metal to be plated on the part). The anode and cathode are both connected to an external supply of direct current. The anode is connected to the positive terminal of the supply, and the cathode (article to be plated) is connected to the negative terminal. When the external power supply is switched on, the metal at the anode migrates to cathode.
The metal used as an anode, can be different types, from precious metals to very common ones:
- Copper – a very difficult metal to be plated, due to the fact that leaves imperfections to the plated surface;
- Silver plating – used in jewelry industry for plating cooper and for applications in electronics;
- Gold plating – used in jewelry industry for plating mostly cooper and silver;
- Rhodium plating – used in jewelry industry for plating white gold, silver or copper and its alloys;
Zinc plating – used to protect the metal from oxidation.