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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Plating onto Cobalt -- adhesion problem
Q. I am currently Nickel electroplating using a Watts bath on to a Cobalt Alloy and diffusing the plate in the surface. However post diffusion there appears to be bubbling of the plate in a random fashion. Anyone any ideas why this happening
Base material?
Surface preparation?
U.K.
1999
A. Many cobalt alloys, like nickel alloys, require a Woods nickel strike for excellent adhesion. The surface might not be properly activated.
Excessive brighteners in a Watts bath can cause blistering, but it would not normally be "random"
- Navarre, Florida
1999
Q. I realize that most copper plating is done on steel or iron. I have a cobalt alloy that I would like to plate, or at least try to plate. I am trying to use copper plating as a method for cleanliness measurement on fine wire. (i.e. less plating=more contamination)
Will the copper plate out on the cobalt (35% nickel) alloy?
Thanks,
- Plymouth, Minnesota, USA
2002
A. Andrew,
I have a doubt, when you say "use copper plating as a measurement of cleanness", do you mean immersion plating of copper from an acid sulphate formula? If so, then the answer is no. Cobalt will not reduce copper from a conventional acid sulphate solution because of its natural passive surface. If you try to remove this passive layer you will disturb your experiment.
Monterrey, NL, Mexico
2002
Q. Guillermo,
Thanks for the speedy reply! Yes I am referring to acidic sulphate solution, unfortunately. Can you tell me of any plating processes that may work on the cobalt wire?
- Plymouth, Minnesota
2002
A. Cobalt nickel alloys require a Woods nickel strike or a low pH sulfamate nickel strike. Clean, acid dip rinsing after each step, nickel strike 40-100 Amps/sq ft. 1 to 2 minutes. Rinse and transfer quickly to desired plating solution, making contact first so that plating starts as the part is immersed in the plating solution.
The woods nickel strike consists of 32 oz/gal nickel chloride and 12 fl oz/gallon of concentrated hydrochloric acid. If you are interested in the low pH sulfamate nickel strike (used on a wider variety of alloys) I can provide it.
Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2002
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