Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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EN Nickel delaminating
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.
plating shop - Honiton, Devon, England
June 2, 2017
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
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,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 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 2, 2017
A. Did you make a replenishment or ammonia ⇦this on eBay or Amazon [affil links] 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 GroutLitron, Inc - Agawam, Massachusetts, USA
June 7, 2017
Thanks Jameson, I will look into this and see if this is a possible cause
- Honiton, Devon,England
June 14, 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.
Popatbhai B. Patel
electroplating consultant - Roseville, Michigan
August 29, 2017
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!
TEL - N FERRARIS - Cañuelas, Buenos Aires, Argentina
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