Electro-chemical Plating and Galvanising
Electroplating is the process of using electrical current to coat an electrically conductive object with a relatively thin layer of metal. The primary application of electroplating deposits a layer of a metal having some desired property (e.g., abrasion and wear resistance, corrosion protection, lubricity, improvement of aesthetic qualities, etc.) onto a surface lacking that property. Another application uses electroplating to build up thickness on undersized parts.
The process used in electroplating is called electrodeposition. It is analogous to a galvanic or electrochemical cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution containing one or more metal salts as well as other ions that permit the flow of electricity. A rectifier supplies a direct current to the cathode causing the metal ions in solution to lose their charge and plate out on the cathode. As the electrical current flows through the circuit, the anode slowly dissolves and replenishes the ions in the bath.
Other electroplating processes may use a nonconsumable anode such as lead. In these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution.