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Etching titanium without Hydrofluoric acid

Q. Hi. I am a Masters student in Chemical Engineering. I am working with the Titanium alloys especially Ti-6Al-4V. Earlier I used 50% Hydrofluoric acid to etch Ti-6Al-4V, but now I wanted to replace it with some other etchant because of its hazardous nature. Can anyone suggest an Etchant which does not involve HF acid.

Praveen Reddy K Depa
- Kingston, Rhode Island

A. Try replacing the hydrofluoric acid with Ammonium Bifluoride

Gene Packman
process supplier - Great Neck, New York

Hydrofluoric acid burns left and right hands, two views, burned index fingers

Never have HF anywhere without antidote on hand!

Calcium Gluconate
for HF acid burns

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The use of Ammonium Bifluoride (ABF) in place of Hydrofluoric Acid can be deceptively dangerous as, in H2O, the ABF will cleave a hydrogen fluoride molecule creating hydrofluoric acid. . . the concentration of HF acid will be proportionate to the amount of ABF in solution and the ratio (20/57) of molecular weights. This is not a safe solution as many have been burned, some seriously with ABF solutions.

I would be extremely cautious in using ammonium bifluoride as a substitute for HF since, upon solubilizing, it springs an HF molecule. The resulting HF concentration will be ~1/3 of the original Ammonium Bifluoride concentration.

Also, if using ammonium fluoride (AF) in an acid medium (i.e., HCl) the H+ ions will convert the fluoride to HF. This is common technology used in oil-well regeneration (in silica media)as AF and HCl are simultaneously pumped "down hole" with the evolution of HF in a safer (down hole) environment.

Mike Berg
fluoride chemicals - St Louis, Missouri

A. Try oxalic acid [affil links] as an alternative. It must be fairly concentrated, and used at an elevated temperature, but it does a very nice job of etching the surface of titanium. You will make titanium oxalate as a by-product, which should be disposed of as required.

tom baker
Tom Baker
wastewater treatment specialist - Warminster, Pennsylvania

Q. This a is a query to Mr. Tom Baker who suggested using oxalic acid to etch titanium: Do you know of any way to extract the titanium oxalate from the oxalic acid solution after etching? We need titanium oxalate for an experiment and it doesn't seem to be commercially available.

William B Hankins
gov't - Menlo Park, California

Q. I was hoping that Tom Baker could give some more details on etching with oxalic acid. My company uses a 10% oxalic acid solution and applies 12V DC current for 30-40 seconds (at room temp.) with results good enough to measure weld penetration on 300 series and 17-4 SS as well as MP35N. Using these settings for Ti, I get a copper-like surface with no indication of the weld nugget for penetration measurements. Are there any recommendations as to how I can improve my etching using oxalic acid at room temp?

Our company is not set up for major chemical handling, so I am looking for something that can be applied fairly easily with minimal equipment (room temp solutions ideal!). As such, hydrofluoric acid is simply out of the question for our facility.

Brian Girouard
Mechanical Engineer - Burlington, Massachusetts
December 1, 2008

Q. Dear Everybody,

I can see a lot of people have successfully tried Oxalic acid to etch Titanium. I would like to know the exact process to do that so that I can try it on my CP grade 2 Titanium. Thank you

Darpan Shidid
Student - Melbourne, Victoria, Australia
May 26, 2010

A. Reducing acids such as HCl and H2SO4 can be used as well as oxalic acid to etch titanium. Usually, you'll need elevated temperatures say 80~100 °C and fairly strong acid concentrations.They have the advantage of being much faster than oxalic.

Barry Martin
- Concord, Ohio

Q. If using HCl and H2SO4 to etch titanium, could Mr.Barry Martin suggest the etching time, etchant concentration, and etching procedure? We need the information.

Leo Wu
- Taipei, Taiwan

A. We have successfully tried the hot sulfuric acid (temperature - 125 °C) with a spoon of ammonium persulphate during every cleaning /etching step to remove the titanium.

- Delhi, India

A. See letter 13456.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

A. I recall an expired patent describing the use of hydrogen peroxide with ETDA, usually at about 50 °C. Etching is slow.

Ammonium fluoride or bifluoride is also slow since the dissociation constant of NH4F is 5 orders lower than that of HF. Some ammonium fluoride based etchants use the addition of nitric acid -- that just bumps the fluoride ion concentration as well as providing an oxidizing agent and lowering the pH. One can argue the safety hazard of this mixture may be worse than using HF. The danger in HF is really the fluoride ions which are easily absorbed through the skin and forms insoluble fluorides of calcium. Care should also be used when handling ammonium fluoride.

Ian Yee
- Austin, Texas

A. For etching ti6al4v 10% HF, 5% HNO3 and 92% H2O with 10-20 sec immersion etching is the best way from my experience.

Venugopal K. A.
- India

A. Try ammonium hydroxide, hydrogen peroxide, and water. Use volumes of 1:1:5. Maybe too vigorous if so then add additional water. Worked on removing titanium from evaporation systems.

Tim Dennis
ceramics - Bloomdale, Ohio

Q. Hi, I'm MOHIT DUDANI from CHENNAI, India. Am trying to figure out the effect of acid treatment on titanium. Working presently with HF, H2SO4 and HCl acids. Can anyone please give me info on the effects of each acid on titanium and concentration used?

Mohit T. Dudani
student - Chennai, Tamil Nadu, India

Hello, Mohit. Since you are working with these acids on titanium, please briefly summarize what you are learning from your own experiments and try to phrase your questions in terms of the answers already provided. That way it is much more likely that someone will share their findings with you, and we'll have a clearer picture of what your issues are too. Thanks.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Q. Has anyone evaluated off the shelf products like Semco Pasa-Jell 107 or Turco 5578L. I am trying to etch titanium for bonding but having trouble finding a supplier for small quantities.

Jeff Lammers
- Melbourne, Florida

Ed. note: Local distributors of your plating processes are usually the best source for small quantities, as one of their services is often splitting manufacturer minimums across several customers. Sorry, but with the anonymity of the internet, asking for evaluations of brand-name products has repeatedly led shills to post as satisfied customers with fictitious names. Comparing brands has proven to be a bad topic , and we don't do it anymore. Apologies :-)

Q. I recently started an assignment with the Center to assist in a project regarding removal of titanium from a HF/HNO3 chemical milling bath. I am particularly interested in learning about titanium chemistry in this environment to understand the various complexes that can form. Any information to lead me to this information would be very much appreciated.

Dick Poduska
- Rochester, New York
November 21, 2008

A. I have used Multi-Etch for titanium production. It's a non-acid (pH 6.8) alternative to hydrofluoric acid. I used it to etch titanium in my jewelry making facility.

cary brief
kind goods - raleigh North Carolina
September 19, 2012

Q. Hi all,
I made a mould for titanium sample. But it is difficult to measure alfa layer (Measuring with microscope).
Shall we etch with 5% NITOL solution? (5% HNO3 + Ethyl Alchohol)

- Chennai, India
October 12, 2010

Q. Hi everybody,
I am a master student in chemical engineering and I work for a company specialized in surface treatment of titanium.
I am looking for a pre-treatment of titanium before anodizing, acid free and that could be used at room temperature. Can anyone suggest such an etchant?

Anne-Lise Jolly
- Aquitaine, France
May 27, 2013

A. Potassium hydroxide + hydrogen peroxide. I don't recall the concentrations. Room temp. Works slowly, depending on your need, perhaps several hours.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina
May 30, 2013

Q. Seems promising. However, for an industrial process, isn't it a risk of hydrogen peroxide decomposition, that could lower the efficiency?

Anne-Lise Jolly
- Aquitaine, France
June 3, 2013

A. Anne-Lise,
Is blasting an option for you? I have found blasting to be very effective as a pre-treatment for Ti.

blake kneedler
Blake Kneedler
Feather Hollow Eng. - Stockton, California
September 9, 2013

A. Are you talking about electropolishing or etching to reveal grain structure? There are some methods to etch without strong acids, but in room temperature it will take longer to remove required material.

Anna Berkovich
Russamer Lab
supporting advertiser
Pittsburgh, Pennsylvania
russamer labs banner
September 10, 2013

Soft removal of oxide from titanium transistors

Q. Hi. I am actually looking for a soft method to remove the oxide layer deposited on titanium electrodes on carbon nanotube field effect transistors. Those transistors were fabricated two years ago, and now an oxide layer is deposited on the 50nm titanium electrodes. As a consequence, the electrical resistance is very high and the transistors are not usable anymore.
Do you have an idea of which kind of treatment I could perform to recover the initial conductance of those transistors?
I already perform thermal annealing, and recover partially the current, but it doesn't appear to be sufficient.
Thanks in advance!

Beatrice Vanhorenbeke
- Montreal, QC, Canada
May 26, 2014

A. Plasma cleaning under a mixture of hydrogen and argon plasma might be useful.

H.R. Prabhakara - Consultant
Bangalore Plasmatek - Bangalore Karnataka India
May 26, 2014

A. The use of Kroll's reagent is best for etching titanium alloys.

Swati suman
January 2, 2015

A. While I agree Krolls reagent is best for Titanium Etching, I have seen a couple of accidents using HF as an etchant.

For those who like to etch titanium without the dangers of handling HF, you can use a mix of Sodium fluoride and Natrium Fluoride. I am not sure what the correct amount should be.

This mix is also sold as multi-etch (in USA) and super-etch (in Europe).

George zimtamwe
- Bonn, Germany
June 12, 2016

A. I have used titanetch (brand name) for my titanium etching. It is similar to Multi-etch, and is sold in Europe. It doesn't use Hydrofluoric acid and is relatively safe in use. I've had great results using this product for some bolts on my bike!

Laurnes Leenders
- Arnhem, Gelderland, The Netherlands
July 1, 2016

Titanium Etch pre FPI

Q. Hello,

I was wanting to know what recommendations anyone has for etching titanium alloys prior to performing penetrant inspection. Looking for about .00025" removal. My company has done this in the past, but in a solution of 50% nitric mixed with ammonium bifluoride etch salts. My concern with the current method is that there is a black residue, similar to smut, that we end up having to wipe off manually. From a fundamental standpoint, to me, wiping a workpiece like this to remove residue can end up smearing contaminants over the surface of the metal that were trying to be removed in the first place. Any thoughts?



Brandon Mascoe
NDT/coating technician - Indianapolis, Indiana
August 20, 2017

thumbs up sign  I was looking for an etchant for Titanium that didn't require HF acid. One of the posts recommended trying Oxalic acid. So I used a 50% Oxalic acid solution for 1 minute at 12 VDC and the grains came out fantastic.

Peter Webster
- Corning, New York, United States
December 11, 2017

A. I have successfully used Oxy-clean with very hot water and a decent amount of time. It doesn't etch as much as it oxidizes the titanium. I've done this then tumbled titanium for an aged effect.

Chris Reeves
- Virginia, USA
March 2, 2018

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