Metal finishing Q&As since 1989

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My Nickel anodes are getting black in bright nickel tank.

We are doing bicycle rims in semi-submerged form. We have noticed that of late the bath stops responding after 4-5 hours of working. The plating finish is dull and shows passivity. Very poor chromium reception. We have noticed that the anodes are getting black when this happens. We have tried conventional high & low pH treatments without any luck. What could be the reason.

K. Ramesh
plating shop - Mumbai-India
2005

Very little information. Please tell us what chemistry do you have in the bath, anode-cathode ratio, chloride concentration, type of brighteners, etc.

Guillermo Marrufo
Monterrey, NL, Mexico
2005

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What is the bath composition and what should it be? Are your anodes sulfur depolarised or not? Too many questions and not enough information. It sounds like your anodes are passivating, but without more information no-one can tell. If that is the case, you may need to add chloride to the bath, but if it is a sulphamate bath that is not the best remedy.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2005

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2005

Hello.......
(I hope Mr. Mooney agree with me?)
Its very easy answer.But I don't understood why any body answer this question exactly.There is some reason;check your bath ph value.It must be between 3,8-4,1.If your bath ph value above 5.0 your anodes getting passivated and turns dark and some metallic contaminants getting collapse deep.So you must work between 3,8-4,1 for ph.Secondly,your boric acid value must be between 40-35 gr/lt.If your bath value under 35 gr/lt your anodes getting blackness and it turns dark.You check these.So turn us...

Alaattin Tuna
- Turkey