White stains in electroless nickel plating
A discussion started in 2005 & continuing through 2017
(2005)Q. My company is doing electroless nickel plating on brass. However, we are facing white stain issue more than 10% of total production every day. The all chemical concentrations involve are controlled in the spec. The nickel bath was made up in the past 2 1/2 years. only top up nickel was done. I would like to know does this nickel solution make up life time can contribute to the issue?
Cheng Souk PingPlating company - Penang, Malaysia
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(2005)
A. Unless you are using one of the baths with highly specialized equipment to remove the breakdown products of the hypo, the normal amount of tank turnovers (100% replacement of the nickel ion = one tank turn over) is 4-20 with 8-12 being common. I am rather shocked that you can even plate with a 2.5 year old bath, even at 100% analysis. James Watts- Navarre, Florida (2005) A. When you say all chemical concentrations are in the spec what do you mean, basic chemicals? Do you analyze sodium orthophosphite, deposited phosphorous? Do you keep track of metal turnovers? How do you maintain pH and temperature? Is your work load fairly constant? Two and a half years is quite a long time. Undesirable by-products will keep forming regardless of care taken during the operation. Guillermo MarrufoMonterrey, NL, Mexico |
A. While a 2-1/2 year old bath is quite old and may have been contaminated over the years with any number of things, bath age is normally defined in terms of the amount of nickel that has been plated from it.
A cycle or turnover is that age from plating out the original nickel content of the bath. Most baths contain 6 g/L of Ni. So for them one cycle is when 6 g/L of nickel is consumed and replaced. That is the equivalent of about 6.6 g/L of electroless nickel plated.
Most mid phos type baths only have a life of between 8 and 12 cycles. After that, the amount of orthophosphite and sulfate contamination is so high that the bath becomes quite low and the coating's quality is quite low.
Your white stain may or may not be the result of this contamination.
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Ed. note: It is our sad duty to alert the readers to the passing of Ron Duncan on Dec. 15, 2006. For those who would like to know more about him, a brief obituary opened Update No. 13 of our Metal Finishing Industry Update Podcast. |
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RoHS EN leaves white stain, non-RoHS doesn't
(2005)Q. Having problem plating RoHS EN on 300 Series Stainless Steel 0.4 mm thick cover (Surface 90 mm X 70 mm). Result 80% with white stain. This only happen when I use RoHS EN. If I use non-RoHS EN, there's no white stain found on surface. Anyone can help. Thanks
Stewart [last name deleted for privacy by Editor]Plater - Malaysia
(2005)
A. Interesting, we never encountered white stains on Lead and Cad Free electroless Nickel.
usually are shadows when you have overstabilized bath.
- Toronto, ON, Canada
(2005)
A. Lead and cadmium free EN is less bright than regular EN.
Yet white stains cannot be a result of RoHS EN. Something else must be wrong.
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel
(2005)
Q. This white stain also is new for my chemist. My chemical supplier suspect is the surface too big. Previous we are plating disk clamp (40 mm diameter) and no problem all the time. Recently I try to shake the jig non-stop during EN bath. This only help me to reduce to 50% reject.
Stewart [returning]Plater - Malaysia
(2005)
A. What do you mean by "recently started to shake parts"?
Agitation in EN plating process is mandatory!
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel
August 30, 2013
Q. Hi,
Our company produces Hard Disk Drive components and we have the electroless Nickel Plating process. However, our company has a problem about the white stain and black dot issue on the parts. Example: I run 3 jigs, only 1 jig has this reject. So, if this problem is due to EN bath, why don't 3 jigs have same reject?
Please advice what I can do to prevent this issue and find the root cause.
Regards,
Zana
- Selangor, Malaysia
September 20, 2013
Q. I would like to ask if dried oil on raw material will cause white marks after electroless Nickel process. If so, what are the causes of this occurrence?
Grace J.- Cebu, Phils
White stains in electroless nickel plating of pendants
February 22, 2017
Q. We produce gold plating jewels. Previous to Gold plating we perform the following process:
- Polishing using a motor/lathe and buffing compound
- Electrocleaning with a Buffing compound remover
- Electrocleaning with al alkaline degrease (6v)
- Nickel plating (3 v)
- Gold plating (6 v)
The problem is that we have some white stains in the borders of the pendants. I have modified almost each variable of the process but still have the stains.
Metalsmith - Bogota, Colombia
March 26, 2017
A. Hi Rafael,
I am not sure I understand your question because the title mentions stains on nickel but your post mentions gold as well. Are the stains on the gold or do you see problems prior to Au plate?
Feather Hollow Eng.
Stockton, California
April 19, 2017
Q. Hi Blake. We are having "white" stains in the edges of the jewels during the nickel plating. It is just in the edges. I do not know if the problem is in the previous electro-cleaning process or during the nickel bath. I have pics of these edges:
- Bogota, Colombia
June 2017
A. Hi Rafael. Your title indicated that you were "electroless nickel plating" these items, but based on the additional info you've provided, I'm leaning towards thinking that this was perhaps a typographical error and you meant "electrolytic nickel plating"?
Although it's hard to photograph brightwork, so pictures can be hard to read, this looks and sounds like classic "burning" to me -- that is, the edges are receiving excessive current density, beyond that at which satisfactory plating can occur. More agitation and/or lower current (voltage) is the first thing I'd look at. Good luck.
Regards,
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"
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