Metal finishing Q&As since 1989

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Silver plating is flaking off of nickel plating

Does anyone know what may of caused gross flaking of silver plate (0.0005") that is plated over nickel sulfamate (0.00015") after a year of parts sitting on a shelf. Parts after plating were visually acceptable. Could hydrogen have caused this if parts were not embrittlement baked?

Jim Steinhoff
Engineering Specialist - Cleveland, Ohio
2004

NO! Nickel is difficult to activate and there are many different approaches to the problem. The longer it sits, the more difficult it is to activate as the nickel oxide layer gets thicker. If you had post plate baked it, you probably could have seen tiny blisters in the silver right after plating.

James Watts
- Navarre, Florida
2004

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2004

If the nickel has set on the shelf for one year it has a tenacious oxide. A cycle to plate anything over this old nickel would be like:

1. Alkaline clean (soak or cathodically) to remove organic soil.
2. Rinse
3. 30 - 50%/vol commercial strength Hydrochloric acid,
4. Rinse,
5. Nickel Chloride (Woods) Strike 6 - 9 volts in 2 pounds per gallon NIckel Chloride with 2 quarts per gallon Hydrochloric Acid for two minutes,
6. Rinse,
7. Silver Strike (0.5 oz.gal Silver Metal with 12 oz/gal Potassium Cyanide),
8. Silver Plate.
9. Rinse,
10 Rinse,
11. Dip in 2%/vol 66 baumé Sulfuric Acid (Cyanide will never "rinse off" you must neutralize in weak acid).,
12. Rinse,
13. Hot Water Rinse.

Then you cannot chisel it off !

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina