MadSci Network: Engineering

Re: electroplating - what should be the anode made up of?

Date: Mon Nov 9 16:18:34 2009
Posted By: Joseph Weeks, Engineer
Area of science: Engineering
ID: 1253957610.Eg

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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