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Letter 41057
Brown Spots appear 1 week after nickel
electro-plating on brass coils
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Hi folks,
I have some age old problems with nickel electroplating on Brass
coil.
After send in for plating, there are brownish/ yellowish spots
erupting rom the surface.
I wonder if it is plating or material problems?
The plater told me its the pores of the brass coil and the sulphuric
acid can't even clean away the impuriites but "trapped" in the tiny
grains of the material and start appearing as yellow spots...
Is that a feasible?
I have seen black and white spots appearing on the coils 2 to 3 years
ago but never see yellow spots before...
Hope some of you can assist me with this long pressing problems.
Yours sincerely,
Alan Chow
Coil Slitting - Singapore
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Hi Alan,
It is very possible what the plater is saying is correct, but it
sounds like they could be using a better pre-dip than sulfuric acid
or a sulfuric acid based pre-dip. There are proprietary peroxide
based dips that offer different degrees of etching and brightness,
and are easy to waste treat. They do a great job in cleaning the
surface of the brass. What is the thickness of the nickel plate?
Insufficient plating thickness could also be a cause of the problem.
The plater should be investigating better cleaning techniques and try
to solve the problem, rather than inferring "it's the nature of the
beast". You could try sending a sample lot to a reputable plater, and
let them know the problems you currently have. If they want your
business they will do everything to get it right. Good Luck!
Mark Baker
Process Engineer - Syracuse, New York
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Dear Mark Baker,
Thanks for your advice & expertise.
Instead of using 1.27um Nickel, we are only adopting 0.5 um Nickel
undercoat before adding Bright Tin.
Is that the industry standards of using 1.27 um for Nickel undercoat
in order to cover colored spots?
We do not have black spots erupting , my old samples tat are 2 years
back did not show any signs of spots erupting....
I need your advice... it may be coil material or cleaning
agent?
Yours sincerely
Alan
Coil Center
Alan Chow
- Singapore
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You have simple galvanic corrsion setting up in the pits. YOu may
retard this tendency by dipping in a weak solution of hex chromi
acid. The rinse following a chromate or chrome plate will greatly
reduce the tendency for these pits to bloom. The brown color is
copper oxide diulted with the zinc and nickel salts in the area.
HOt-cold-hot-cold rinsing before dippping in the chromic acid will
further increase the protection.
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Hello again Alan,
In your first posted question you had said "send in for plating".
Does your company have it's own plating department or are you using a
jobshop plater? The reason I ask is to determine how much control you
actually have to rectify this problem. If you have your own plating
shop, the responses given on this site can be implemented by you or
your plating manager. As Mr. Probert and I have mentioned the problem
stems from the substrate material (brass). To alter the types of
plating and the thickness of the Ni, is like putting on a band-aid,
hoping to stop the bleeding. The issue of pore corrosion has to be
dealt with first. Reducing the Ni thickness to 0.5um is not a good
idea regardless of what the final plate is. I would concentrate on
the pre-plate cleaning cycle, before you change anything else. You've
been given a few recommendations to begin with. Good luck!
Mark Baker
Process Engineer - Syracuse, New York
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