Metal finishing Q&As since 1989

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Nickel going passive

My name is Don and I run a plating shop in California. For many years we were able to take parts out of the nickel and go directly from the clean rinse to the chrome bath without any problems. Several years ago we made a new chrome bath and now we can no longer go direct from the rinse, instead we have to re-activate the nickel in an acid bath as well as the chrome rinse before chroming. If we do not our parts will have dark brown splotches. I was told that this is the nickel going passive. We have tried to increase and decrease the amount of brighteners in the nickel bath as well as raising and lowering the ph. We also made a special clean water rinse to make sure we were not introducing nickel chloride on the parts into the chrome and nothing works. any suggestions will be appreciated.

Thanks,

Don Prestage
Owner - Escondido, California
2007

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It's not only that the nickel is "going passive" it is the chromium that is "getting old".
I will explain myself:
If it was coming from nickel passivation then you would get "white wash" problem, gray spots. But your problem is brown spots. Brown spots can come as a result of incorrect ratio of the chromium solution ingredients and from too high metal impurities.
How high is your Chromic acid concentration? I would suggest to operate at maximum Chromic acid concentration, at least 300-325 g/l

Sara Michaeli
Tel-Aviv-Yafo, Israel
2007