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"pH rise in nickel electrolysis"

February 17, 2010

Hi I am Ben, I have a problem with our electrolysis experiment. The pH rises abnormally in the cathode, I just want to know how to solve this problem?

Ben D.
analyst - Philippines

February 17, 2010

Hi, Ben. You have identified yourself as a K-12 grade student, but I'm not really sure if this is a student electrolysis experiment or a practical problem in a plating shop. If the latter, please patiently search the site as there are about a dozen threads on the subject.

But the answer for a student is that some of the electricity goes toward hydrolyzing water into H2 gas (which escapes as bubbles) and OH- ion (which causes the rise in pH). The best cure for a student is to electroplate at a lower voltage. Good luck.


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

February 18, 2010

Do you mean electroplate or electrolysis of water into the two gasses?
For the plating, if you do not want the pH to rise, you need to keep the cathode voltage below the hydrogen overvoltage potential. Obviously, this would not work for generating H and O gasses.
The solution is to add an appropriate amount of acids, like sulfuric or sulfamic. Do not use halogen acids as they will give off halogens with the O2.

James Watts
- Navarre, Florida

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