|MadSci Network: Chemistry|
Dear Mr.Khawevh, In electroplating this kind of problem is common. It is called poor "throwing". if you have an encyclopedia available, look up "electroplating". The electrical current is what carries the Cu ions through the solution to the surface of the cathode electrode, in your case the cathode is a spoon.. The current must get equally to all surfaces of the cathode for an even plating. Consider an exaggerated situation. Instead of a spoon, you wish to plate all surfaces, inside and outside, of a small section of tubing. The piece of tubing is hung in the solution and the currrent is applied. The current will go to the outer surface of the tubing, but very little will go to the inside. The current will always travel by way of the shortest path, that of least resistance. Also, when the copper is plated out of the solution, the solution is depleted of copper in that area, and of course no more can plate out. Outside the tube, normal circulation. etc. will bring in fresh copper solution. Inside the tube, there will be not only very litle electrical current, but very little replacement of any copper that had plated out. One question I have is, what is the exact arrangement of your electroplating cell? How far fron the anode is the cathode [the spoon]? What side of the spoon faces the anode,is it the convex, or concave sides or the edge? If you place the concave side close to the anode you may be able to plate it as well as the convex side. What is the shape of the anode? Maybe make the anode in the shape of a ring, with the spoon [cathode] in the middle of the ring. Then maybe all surfaces will then be plated equally. One experiment may show you what is happening. Obtain an ohm-meter. Disconnect the electric current supply from the plating cell. Measure the resistance between the anode and various points in the plating bath, including the convex and concave areas of the spoon and the electrolyte close to these areas. Regards, Charlie Crutchfield
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