|MadSci Network: Engineering|
In electroplating, metals are deposited on a cathode by running an electric current between an anode and a cathode. Electrons reduce the metal ion to the base metal at the cathode. The reverse can happen at the anode. Electrons are removed from the metal, and the metal dissolves into the electroplating bath, becoming a metal ion. The metal ions present in the electroplating solution can come from a metal salt used in making up the solution, and from the metal anode which gradually dissolves as the electroplating process takes place. If the anode is the same metal that is being plated, then the concentration of metal ions in the solution remain at the same concentration. If the anode is a different metal (say one that doesn't dissolve) then over time, the metal ions in the solution will decrease in quantity until the electroplating bath is exhausted. From a practical point of view, the metal containing chemicals used to make up an electroplating bath are often more expensive than the base metal used in the cathode, so it is often more economical to use an anode of the same metal being plated. Also, with a metal anode, if the concentration of metal in the bath remains essentially constant, then day after day, the same operating times and voltages can be used to produce the same coating. If the concentration of the electroplating bath is changing, then the times and voltages that worked yesterday may not work today. Thanks for your question.
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