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Cadmium plating on tungsten
Q. Does anyone have data on corrosion resistance of tungsten heavy metal alloys (90-95%W, remainder Fe and Ni)? Aerospace standards frequently call for cadmium plating and or/paint finishing of parts such as counterweights. Our experience is that corrosion of these alloys is rare and only occurs under extreme conditions.
Aryeh Asher- Ashkelon, Israel
1999
A. Are you looking for information on the corrosion resistance of untreated tungsten heavy metal alloys, or for cadmium plated/paint finishing of these alloys? Under what service conditions?
If some organization has specified cadmium plating for the application, there is usually a good reason. Cadmium evaporates in the heat and vacuum of space, so I suppose the cadmium is for some lubricity or corrosion characteristic at standard temperature and pressure.
What do you mean by extreme conditions? Unless we know the application, it is difficult to answer the question.
Regards,
Tom Pullizzi
Falls Township, Pennsylvania
Q. We found out that Tungsten Alloy (95%W-3%Ni-2%Cu) with nickel electroplating were corroding after going through the damp tests for about 14 days. What causes the tungsten metal to corrode? Is it due to insufficient nickel coating that eventually results in corrosion.
Lau shir ling- Singapore
2001
A. Hi Lau,
Thin nickel plating can be porous or even pinholed. If so, it can accelerate corrosion due to galvanic incompatibility rather than retard it. Even 20 microns is only good for moderate corrosive conditions, and that's on smooth, polished metal. If the surface is rough, you need heavier plating. What thickness are you applying and have you by any chance done cross-section micrographs that might give an indication of how the nickel is depositing in this application? Thanks!
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. I am trying to cadmium plate tungsten, and have had blisters and adhesion issues the whole time. I am using a nickel strike as my activation process. If anyone has any helpful info please let me know. I can use all the help I can get. Thanks
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plating shop employee - Fenton, Missouri
October 20, 2010
A. Hi, Tom
Tungsten is a refractory metal which is exceptionally difficult to properly activate for good adhesion. But the ASM Metals Handbook, vol. 5 ⇨
has an entire chapter on the subject of properly prepping & plating these refractory metals. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Multiple threads merged: please forgive chronology errors and repetition 🙂
Q. Hello, my question pertains to cadmium plating different types of tungsten. I have some tungsten parts I need to machine and they require a cadmium plating after completion.
The tungsten I am required to use has to meet a MIL-T-21014 Class three specification but from what I am told there are different types of Class 3 tungsten.
Specifically, 95% tungsten, 3.5% Nickel, 1.5% copper or, 95% tungsten, 3.5% Nickel, 1.5% Iron.
Will the cadmium plating work on the copper alloyed tungsten or would it be better to use the iron alloyed tungsten? From my limited dealings with cadmium plating it was always done on ferrous based materials? This would lead me to believe that the copper alloyed tungsten could not be cadmium plated but I am not sure. Thanks for any light you can shed on this.
Fabrication specialist - Elmwood, Nebraska, USA
October 18, 2011
Hi, Curtis. I think it will prove irrelevant whether the 1.5% is copper or iron. Tungsten is a refractory metal which is very difficult to plate onto. But the ASM Metals Handbook Vol. 5 has a chapter on how to pretreat refractory metals for electroplating and may provide good guidance. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi. We've been working with a company who uses WHA's for vibration dampening and employs a 90 wt%W - 6wt% Ni - 4wt% Cu. We discovered through SEM/TEM and EDS that there is actually trace amounts of Fe and C in the matrix phase which binds the W grains together.
Due to the galvanic potentials, the more noble W vs. the matrix causes microgalvanic cells across the whole surface in contact with electrolyte.
We discovered, and verified with research, that any amount of copper in the matrix accelerates the corrosion, vs a matrix with say Ni-Co or Ni-Co-Fe. It's due to the solubility of tungsten in the matrix, where a higher % of W dissolved in the matrix reduces the galvanic potential difference.
Basically, we're looking for ways to finish it as well, and any moisture that touches it starts to eat at it. Unless we can plate it with Al or Cr and passivate it.
- Hamilton, ON, Canada
March 29, 2013
A. Hi Rob,
I have experienced exactly the problem you are seeing now. the galvanic potential of the copper and nickel against the tungsten was setting up corrosion sites and causing the part to bind.
In the end we have electroless nickel plated all over to about 0.002", this solved our problem. There was a lot of work necessary in getting the surface clean and active enough for plating, talk to a reputable plating house in your area and I'm sure they will be able to help you.
Aerospace - Yeovil, Somerset, UK
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