Plating Nickel onto Titanium
Q. I need technical information on electroplating pure gold and palladium onto pure titanium. I understand that you have to clean titanium and you have to protect the surface from oxidizing again before electroplating. can any one help with a proposed cleaning process and plating cycles. Thank youROY CONIGLIONE
A. Hi, Roy. Indeed titanium is very difficult to plate onto because of the tenacious oxide film it forms very quickly. ASM International's "Metals Handbook--Volume 5: Surface Engineering has an outstanding chapter on how to plate onto titanium and other hard to plate metals. But it always involves very aggressive acids, followed by care in quickly get a coating of another metal onto it.
Nickel plating is usually a vital part of the sequence.
In addition, one method/enhancement I know of is to nickel plate the object and then heat it to diffuse the nickel into the titanium. Letter 13456 offers some details on that. Good luck with it.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
A. I would suggest looking into Aurobond TCL Gold Strike (Sel-Rex) for the initial strike for Ti. It has always been superior to Wood's Ni strike for difficult SS plating problems. Sel Rex does recommend it for Ti.Kirk McGlothlan
A. We once plated gold onto Ti wire, we used an existing process we have for plating onto Mo wire
Anneal the wire at 900C at 15 meters/min under H2
0.5 -1.0 micron Flash in Ni Sulphamate... (There is no real need for electrolytic cleaning as this promotes oxide on the Ti)
A gold flash may also help, as when the material is re-annealed a Ni/Au alloy is formed.
Re-Anneal at 1100C at 15/M.Min to diffuse some Ni into the Ti
At this stage check for blistering, if there is still oxide on the Ti, the nickel will not diffuse..
Hope this is of some use...Mike Montgomery
A. How are you you doing the nickel plating on titanium?
Method 1: 1.Alkaline degreasing with 50 g/l NaOH 50 g/l NaCO3 2.Rinse 3.Etching in hydrochloric acid time 3 minutes 4.Rinse in Rochelle salt acid 5. Copper strike 50 g/l and 160 Rochelle salt acid in 5 minutes 0,4 A/dm 6. Rinse in sulfuric acid.
Method 2: 1. Alkaline degreasing with 50g/l NaOH 50g/l NaOH3 2. Rinse 3. Wet blasting with aluminium oxide carefully over the part. 4. Activation 325-450 g/l hydrofluoric acid 3 minutes after gassing. 5. Neutralizing in 50g/l potassium tartrate 6. Copper strike See method 1: After one of these steps you can plate nickel or chromium.
Good Luck to all. Regard Anders. S
3rd Generation in Plating
Consultant - Arvika, Sweden
A. I would suggest that you try the cycles in Electroplating Engineering Handbook edited by L.Durney.
Titanium passivates very rapidly so there can be no delay between tanks.
I assume that you are on 6-4 Ti. Watch your caustic step as it can cause problems by etching out some of the aluminum.worm pitting.
I am in favor of a nickel strike, high acid low nickel and then directly into the nickel plate tank with minimal rinsing.
I wood skip the neutralizing step after the HF activation.
I would also activate in a 35-45% nitric and 4-5% HF. It works fine and is less critical. This chemically polishes as well as activates. If this is too slow, try it in the lab, gradually increasing both acids. 7 nitric to 1 HF is as low as you should go in the ratio, and 14 - 1 is the weakest HF ratio.James Watts
- Navarre, Florida
A. Hi Jim. We already use methods number 1 without no problem. About method number 2 I can see that be wrong with using hydrofluoric acid but I mean hydrochloric acid. We have no problem with etching step. Obvious there exist more ways to do plating on Titanium. I'm going to buy that book you recommend from the book store. Thanks for your answer Jim.
Sundman & Nylander AB
(2000) -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
I am looking into the improvement of my laboratory's ability to plate Ni on to Ti because of we are having problems meeting extremely rigorous adhesion criteria.
At this time our Ti substrate is grit blasted with Al2O3 media, ultrasonically cleaned with alkaline cleaner, etched with 35% HNO3 + 2% HF, and then given a standard Woods Ni strike. After that the parts are electroplated with a few more mils of Ni using a conventional Ni sulfamate bath, and then a final layer of electrodeposited Sn is added to the parts. We are seeing loss of adhesion between the Ti and the Ni.
I spoke with a couple of vendors yesterday (Atotech and Enthone OMI), and they made the following suggestions to improve the adhesion between the Ni and the Ti:
1) Instead of a standard Woods nickel strike, he suggested switching to a nickel bromide strike. He said that since nickel bromide attacks Ti in aqueous solution (quoted Ti basket vendor indications and literature), then it should activate the Ti surface to a greater extent than NiCl strike.
2) Increase the duration of the Ni strike. He said for us to analyze the region of poor adhesion on the Ti part and look for a pincushion effect. If there is a pincushion effect then it is likely from areas of the Ni strike that are not thick enough. This would allow any exposed areas of the Ti to become passivated, and could be easily avoided if we just make the Ni strike thicker.
The vendor from Enthone OMI indicated that we cannot be entirely sure that our problem is between the Ti and the Ni because of how thin a Ni strike typically is. If any passivation occurs to the Ni strike before Ni sulfamate (i.e. while the parts are waiting in a beaker of water) it could be enough to result in poor adhesion between those two layers. As a remedy to this problem he suggested that immediately prior to Ni sulfamate we perform an additional HNO3/HF etch for 10 seconds (or so) followed by a rinse step.
If anyone else has suggestions for my process of plating Ni on to Ti, please let me know.
A. Hi, Chris. Getting adhesion onto titanium isn't easy, as you know. You might want to check Volume 5: Surface Engineering of ASMI's Metals Handbook which suggests immersion in much stronger nitric/hydrofluoric acid than you are using; followed by immersion in a hot and strong dichromate/HF mix; followed by acid copper plating. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Following up on Enthone/OMI's comment; I think in any bonding problem (plating or other) it's important to find to identify the true plane of failure, in this case Ni strike / Ti,or possibly sulfamate Ni / woods Ni. You may save yourself some time and money in the long run by having some elemental analysis run. Most SEMs are equipped with x-ray analysis and x-ray mapping capability. If this is not available in house you might try a local university, or a company that offers analytical services.
This is a fairly routine kind of analysis now.Paul Stransky
- Putnam, Connecticut
A. I have plated nickel on titanium with adhesion values up to 35,000 psi (ring shear test). The process involves grit blasting the titanium, striking in a sulfamate bath and diffusion bonding in a vacuum oven at 1000 C. Works every time.R.D. Mikkola
aerospace - Oak Ridge, Tennessee
Q. I am picking up on the letter from Christian Adams, in which he talks of a Nickel Bromide strike bath. Has anyone the breakdown on this bath, or info. on who sells it?
I believe I used to analyze a nickel bromide bath. I don't remember the concentrations, but the solution looked about the consistency of lime juice, so what would that be, about 1 oz./gallon nickel metal? , I think the bromide will analyze using the usual nickel chloride titration and making the atomic weight adjustment., pH is about 2.0, I believe. Since the bath is thin, use a low current density, you are only using it for activation of the Ti, based on the above answers to the original question.
Correction! D. Gardner Foulke, in "Electroplaters' Process Control Handbook" [link is to product info at Amazon], 1975, Robt. Krieger Publishing, Malabar, Florida, informs me that Bromide will interfere with that chloride analysis, so I guess I used to do the EDTA titration for nickel, and calculate from there.
Falls Township, Pennsylvania
A. Recently we have successfully done nickel plating on titanium alloys. first titanium was pickled with Nitric acid (69%) 3 volumes and HF (60%) one volume until red fumes just evolved. Then component etched with 240 g/l sodium dichromate and 40 ml/l of HF for 20 min at 80 degrees temperature. then immediately carried out nickel plating with normal Watts bath. You will get excellent adhesive nickel plating.B.V. Subba Rao
- Hyderabad, Andhra Pradesh, India
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