Answer to Question #25063 in Inorganic Chemistry for Tabish
explain the flowchart of electropalting and anodizing?
Anodizing increases the thickness of the naturally occurring oxide coating on a metal. Electroplating adds a coating of a different metal to the surface. Anodizing only works for metals which form corrosion resistant oxides that tightly adhere to the base metal surface, like aluminum. Iron oxide, rust, flakes off, so steel cannot be anodized. Example of flowchart of anodizing process:
Anodizing: Aluminum is immersed in a tank containing an electrolyte having a 15% sulfuric acid concentration. Electric current is passed through the electrolyte and the aluminum is made the anode in this electrolytic cell; the tank is the cathode. Voltage applied across the anode and cathode causes negatively charged anions to migrate to the anode where the oxygen in the anions combines with the aluminum to form aluminum oxide (Al2O3).
In electroplating : The anode and cathode in the electroplating cell are both connected to an external supply of direct current — a battery or, more commonly, a rectifier. 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 is oxidized from the zero valence state to form cations with a positive charge. These cations associate with the anions in the solution. The cations are reduced at the cathode to deposit in the metallic, zero valence state.
Example of flowchart of electroplating process: Copper is oxidized at the anode to Cu2+ by losing two electrons in acid solution. The Cu2+ associates with the anion SO42- in the solution to form copper sulfate. At the cathode, the Cu2+ is reduced to metallic copper by gaining two electrons. The result is the effective transfer of copper from the anode source to a plate covering the cathode.