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Cyanide Copper Plating question: Bath seems to plate properly, but Hull Cell panels are dull at extremes

Q. I am doing copper plating with alkaline cyanide (that is CuCN and NaCN) and got satisfactory results (at least it appears satisfactory) -- but when I did Hull Cell test then I got dullness on high current density area and low current density area. After making volumetric analysis I have adjusted the concentration of copper and free cyanide ... then the dullness at LCD area increased ... then I have using additives by which I got very less area as dull on LCD and bright from HCD to centre ...
P.S.: let me know what is the reason for dullness on these extreme areas and how I solve these problem to get my bath at optimum efficiency

Azhar Ali
process engg. - Lahor, Pakistan
2007

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A general pointer is that potassium baths will have a broader bright plating range than sodium baths, Azhar. But you should not expect a perfect Hull Cell panel all the way from LCD to HCD, you'll usually have a little dullness at the LCD end -- if you didn't have any problems at either extreme, the test would be less satisfactory as a tool. It sounds like you achieved this situation after your final adjustments unless I misread.

If you can find a copy of the AESF Illustrated Lecture by Don Swalheim on "Cyanide Copper Plating"*, it includes a number of Hull Cell panels for different situations that may give you a clue towards troubleshooting various problems. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

* - The "Illustrated Lecture" series were sets of 35 mm slides and instruction booklets. You might contact the National Association of Surface Finishers at www.nasf.org and see if they have any of these illustrated lectures left in their bookstore. For readers from the USA, many local branches of the AESF may have a copy; finding them in Pakistan may prove difficult or impossible though. Fortunately, the same information, including the pictures of the Hull Cell panels, has been incorporated into the NASF training CEF training course.

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Dear Azhar,
The reason for dullness in the LCD in mainly due to poor throw of plating. Please check the back side of the panel, if the throw on the back side is quite ok, then increase the cyanide conc. and additives say 0.05ml/L. Please do check the ratio between anode and cathode. Make sure of all the parameters for the electrolyte are under optimum conditions

Shafiuddin A. Mohammed
metal coating shop - Dubai, United Arab Emirates
2007