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Pickling of titanium

2007

I am a quality consultant to a firm that processes titanium scrap from aerospace products (croppings, trimmings, etc. A percentage of these require pickling and currently in use is Nitric/Hydrofluoric.
Are there any known alternatives to this at this time that are commercially viable?
Thank You in advance for any information on this subject.
Bill Dorman

William M. Dorman
- Cassadaga, New York

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2007

Bill:

Use of citric acid based passivation solutions with ammonium bifluoride will successfully etch titanium or austenitic stainless steels when used at specified temperatures at slightly longer durations.

Thanks, Daryl.

Daryl L. Roll
Costa Mesa, California, USA

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20 gms/l Hydrogen peroxide will dissolve titanium oxide (and nitride) and leave a clean titanium surface. The solution I used was at pH7 - 9 because I did not want to attack other metals present. Sodium pyrophosphate is a suitable pH buffer. The solution can be used cold overnight or hot for an hour or two. The hydrogen peroxide decomposes so you will need to make additions of about 10 mls/litre every few hours especially if hot. The dissolved titanium is a yellow colour in the presence of hydrogen peroxide so if your solution was working but has become colourless it is time to add some more hydrogen peroxide.
The titanium metal itself is not attacked at all so I am not sure if this helps. Nick

Nick Clatworthy
- Whitstable, Kent, UK
2007