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topic 60460

EN Nickel delaminating


June 2, 2017

Q. We are plating EN medium phos approx. 25 microns onto aluminium followed by 0.5 - 1 micron of soft gold all over. We are getting the EN delaminating from itself; and on a tape test, the gold comes off with Ni attached but does not leave a bare area of Al, but a Ni plated area.
How can the Ni delaminate from itself? Any thoughts would be appreciated.

Steve Britton
plating shop - Honiton, Devon, England
  ^- Privately contact this inquirer -^


June 2017

A. Hi Steve. And you're sure nobody pulled these parts out to measure them or change a filter or replenish, and then put them back after they became passive?

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


June 2, 2017

Q. Sadly I am sure of this. We repeated the process and got the same result.

Steve Britton [returning]
plating shop - Honiton, Devon, England


June 7, 2017

A. Did you make a replenishment or ammonia add, or potentially have a temperature swing while these parts were plating? Large swing in plating rate from a parameter change can cause Ni delamination from itself, especially when put under stress later (such as the soft gold layer).

Jameson Grout
Litron, Inc - Agawam, Massachusetts, USA


June 14, 2017

thumbs up sign Thanks Jameson, I will look into this and see if this is a possible cause

Steve Britton
- Honiton, Devon,England


August 29, 2017

A. Steve,
Delaminating EN, delaminating nickel over nickel or base metal to EN? If base metal to EN: Contamination prior to EN or you do not have good activation. EN to EN: Check EN chemistry.

popat patel
Popat Patel
    Howard Finishing
Roseville, Michigan



August 29, 2017

Hi Elliot!

I would say that the coating was damaged when the bolts were installed. Organic coatings like Dacromet don't have the self repair capacity of a hot dip galvanized bolt, and when a bolt is damaged, corrosion may get through.

For this usage, I (and many others may say the same) recommend hot dip galvanization bolts and nuts. Lab results may say differently, but in practice damage in the bolts thread is almost impossible to avoid.

Best of lucks!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina



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