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topic 0897

Electropolishing Nitinol nickel-titanium alloy


A discussion started in 1997 but continuing through 2019

1997

Q. I am currently working on a process to electropolish Nitinol (Ni, Ti alloy) to a highly finished surface. If you have any suggestions regarding the chemicals and equipment I should consider using, please tell me. Thanks!

Jingli Wang


1997

A. Depending on the size of your workpiece (anode) and the specifications on your rectifier, you might use phosphoric acid (quite concentrated). But beware: The current densities might be very LARGE, and you will lose weight (from your workpiece) FAST!

Regards,

Jan Morten Sraker


1997

A. Jingli:

For a first information pass, you can find in the USB Library "Electroplating Engineering Handbook" by L.Durney. It has a great chapter on electropolishing various metals and gives formulations, amp/volt functions, calculations, etc. ASM Metals Handbook also has an excellent treatise. Also the Metal Finishing Guidebook is killer. These three references should be enough to get you started. Since you're in Academia I'll give you some math: "The required current density necessary to sustain a polishing condition is inversely proportional to the boundary layer thickness." You can demonstrate this on one of Dr. Newman's RDEs. I'm currently building a medium-size EP facility in Texas. I'll be happy to discuss this further if you need.

Regards,

Dave Kinghorn
Dave Kinghorn
Chemical Engineer
SUNNYvale, California




  -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am interested in getting information about electropolishing nickel-titanium (Nitinol) tubing. What kind of cleaning & preparation would be appropriate? What polishing solution do I need, and any other info for a beginner. Can you help or direct me to help?

ed synder
- san jose, California


1999 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Please, I want information about electropolishing for Ni-Ti alloys.

Thank you advance / Best Regards

Emanoel Ribeiro de Almeida
- Brazil


2006 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Anodizing Nitinol (nickel titanium). I am interested in finding out whether anyone has successfully anodized nickel titanium and what were the results of this.

Glen Roberson
hobbyist - Las Vegas, Nevada


thumbs up sign Hello, gentlemen. As you see, we added your inquiries to the thread of an older letter on this topic, which hopefully answers them, but please expound on your situation if not. Thanks.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


1998

A. My experience is after electropolish you will need to do a fine diamond polish to get a mirror type finish. I was working with .032 and .045 pointed wire

Greg Townsend
- Minneapolis, Minnesota



1998

Q. Since you are specializing in electropolishing Nitinol, I would like to find out about the possibility of using Nitinol as an electrode immersed in blood, but used only as a cathode. Have there been applications in cardiac or other modes of stimulation where Nitinol served as a current carrying electrode without being corroded? It is claimed to be highly bio- and hemocompatible, but what happens when current is passed through it at low densities and in pulses, rather than continuously? Does Nitinol have a protective oxide coating as titanium or is the surface similar to the bulk of the alloy?

Thank you for any info!

Peter Tarjan
- Coral Gables, Florida



1998

Q. I am working on a process to implant ions in Nitinol (Ni, Ti alloy). If you have any information about that ...

Thanks a lot.

Laurent Brault
- France



2006

Q. Hello,
I'm apprentice engineer in materials and I have to perform electropolishing on very small and thin parts made of nitinol. I tried so many times to use the 20% H2SO4 & 80% methanol but it doesn't go well.
I heard that electropolishing can be done in acid-free solution, low voltage. Can someone help me or give me some advices concerning cathode, electrolyte and conditions of the experiments (current density, temperatures or else).

Thank you so much,

Pnina Green
student - Haifa, Israel



Electropolishing of NiTiAu

2007

Q. Dear all,

I am currently looking for a suitable electropolishing solution for the ternary shape-memory alloys TiNiAu in order to have a thinned sample for electron microscopy.

I already tried several solutions that are known to work well with TiNi. Unfortunately, the added gold at a concentration around 15 at% seems to severely hamper the electro-polishing: the same conditions as for Ni-Ti give etched specimens with bad edges of the hole.
We've played with tension, temperature, fluid speed,etc.. but without success.

Solutions tried that work with NiTi but not with my sample:

80% methanol + 20% sulphuric acid (-17°C)
93% acetic acid + 7% perchloric acid (5°C)
93% methanol + 7% perchloric acid (-10°C)
75% methanol + 25% nitric acid (-22°C)

I already looked up in the literature and couldn't find anything close from my alloy. So I was wondering if you might have a suggestion of an alternative, eg, adding an extra acid to one of the above baths or maybe something completely different.

Many thanks in advance,

Rémi Delville

EMAT - Electron Microscopy for Material Science - University of Antwerp, Belgium

Remi DELVILLE
PhD Student - Antwerp, Belgium


December 7, 2009

A. I am polishing(Electro Polishing) NiTi with high surface finish and have been doing for last three years.

Use the following recipe

90% metahnol and 10% perchloric acid solution.

Temp of polishing 0 °C.

18 Volts for 20 secs.

Before Electropolishing, manual polishing followed by diamond polishing

Try it and let me know if it works

Ritwik Basu
- IIT Bombay , Mumbai , INDIA



March 16, 2017

Q. Give me the methods of electropolishing of nitinol stent and heart valve to make surface area clean and smooth. And give the proper parameters of EP. We have the parameters but from that we have not getting proper result so please kindly provide me best parameter.

dheeraj mishra
- vapi,gujrata,indai



April 27, 2011

Q. I am getting up to speed on electropolishing and wondering if anyone can provide (or point me toward) the specific chemical equations for what is actually happening (dissolution of metal at anode, oxide layer formation, side reactions, etc.).

Benjamin Seim
Engineer - Minneapolis, Minnesota, USA



Metal to contact NiTi-anode during electropolishing

October 26, 2017

Q. Hello everybody,

I'm doing my student research project on electropolishing small NiTi structures. I have several electrolytes like sulfuric acid + methanol. As cathode I use stainless steel.

Can someone recommend a metal to me, which is suitable to contact the NiTi workpiece? (The metal is going to be in touch with the electrolyte as well)

Kind regards

Matthias Schwarz
- Germany, Stuttgart


October 2017

A. Hi Matthias. Bare copper rack tips are often used in installations for stainless steel electropolishing, and I'm not immediately seeing any particular reason they cannot be used for electropolishing NiTi in a sulphuric + methanol solution. Except for the exposed racking tips, the rest of the device should probably be made of copper but plastisol coated. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



June 4, 2019

Q. Hi I'm currently working on an electropolishing station for a nitinol implant. I'm using an ethylene glycol solution with a 2% concentration of sulfuric acid and 1 mol of salt, all of the substances reagent grade.
Right now I'm using a stainless steel mesh and platinum coated tweezers as anode and cathode -- are those materials okay?
I'm running at a temp of 20 °C; should I go colder?
For power settings I'm using an amp control with adaptative voltage, should it be the other way around?

Thanks in advance!

Juan

Juan Rodriguez
- Salt Lake City, Utah, USA



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