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How to do NiB electroless plating on top of NiP electroless nickel plating

Q. Hi,
We want to obtain a double layered electroless NiP/NiB coating. We use commercial baths and when we do individual NiP and NiB coatings we have a good surface. But when I put the NiP coated sample (mild steel) in to NiB bath I get smut formation, and no NiB plating is seen on the surface.

Do you have any information about what should I do for obtaining a NiB layer on the NiP coated steel. Should I activate the surface with a chemical such as nitric acid or etc.

Sinem Eraslan
- Istanbul, Turkey
January 18, 2012

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You said you use commercial baths. Your vendor should give you advise, he makes money with you. We won't.
G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
January 24, 2012

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March 10, 2012

EN phos could be contaminated with copper, or the ENB could have copper or other contaminants that cause a smut. Test for impurities (suppliers can help). Also, low reducing agent (dimethyl amineboron) in the NiB solution can cause smut.

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])

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While depositing the Ni-B layer over Ni-P layer, formation of a passive layer on Ni-P might interfere the Ni-B coating.

A nickel strike would help solve this problem.

I did not understand what you mean by SMUT formation.

T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)
March 28, 2012