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Zinc electroplating turns to black

Hi, I am a student. I was working on my school work for a topic electroplating. I use ZnSO4 for my electrolyte but whatever what voltage I put at it will turn to black Immediately. I tried to use other metal to plated at. Like Cu, Fe and Ni but they all turn to black. The second one was the NiSO4. It went black too. ( all the solution is about 1M concentration)
Did I made any mistake? or can you please tell me what is the correct way to do it.

Frank L.
student - UK
2007

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You probably need to add some sulfuric acid to reduce the pH a bit, and you probably are using a voltage that is too high even at the lowest setting you tried. A more dilute solution may help as well. Try doing it per our FAQ. Good luck.

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