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topic 5953

Unacceptable Nodule Formation In Hard Chrome Plating


(2000)

I WORK IN A HARD CHROME PLATING PLANT IN VENEZUELA FOR SEVERAL YEARS AND ALWAYS OBSERVED THE ACCUMULATION OF NODULES ON THE ENDS OF THE PIECES THAT WE HARD CHROME PLATE. MY QUESTION IS, HOW COULD I AVOID OR REDUCE THIS EFFECT TO MINIMUM? IS IT UNAVOIDABLE?

Jhonny Chirinos
Cromado Duro c.a. - Barquisimeto, Lara. Venezuela


(2000)

While you could try PVC "shields" near the ends of the pieces, to try to steer the current away from the high current density corners, you may achieve only partial success. Usually, the best way to eliminate nodules on corners is with conductive "thieves" or "robbers" that absorb most of the plating that would otherwise form on the corners.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2000)

In addition to Ted's comments, having a generous radius on the ends (eliminate sharp corners) helps a great deal.

I assume that you are using tank anodes rather than conforming anodes. If they were conforming, you could chrome plate faster because of a smaller anode to cathode distance, increase the plating efficiency, and reduce the amount of anode near the ends so it would plate more uniformally, thus less after plate grinding.

Shielding the part normally works better than shielding the tank anodes.

James Watts
- Navarre, Florida



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