Passivation/Pickling of Titanium

groags · Sep 24, 2003

Hi,
I am looking at ways of temporarily decommissioning (for 3 months) a Titanium Grade 17 autoclave. The autoclave is in service for Pressure Acid leaching of Nickel laterite ore. The conditions are 45 g/L sulphuric acid at 250 degrees C with 70 g/L chlorides.

Does the titanium need to be pickled/passivated ? or is there any other form of protection needed for the titanium to keep its condition for 3 months ? and if so how do you perform this protection?

I would apprecaite any advice.

Thanks,
Ronan

unclesyd · Sep 25, 2003

We have quite a few Titanium vessels in mainly HNO3/Organic acid service and have not had problems with any after cleaning, say with water, and letting them sit. If we have it open we leave it open and if closed it stays closed. The same can be said for numerous heat exchangers. We have had no problems with Titanium setting for any period of time if cleaned. I wouldn’t leave any heal in the vessel though.

Exposure to air helps with Titanium equipment. Some of this equipment has been in service for 40+ years.

TAHX · Nov 11, 2003

The oxide film on Titanium naturally occurs. It is about 12 to 16 Angstroms thick immediately after being pickled. It grows to about 50 Angstroms in 70 days. 100 Angstoms in a couple years. The film growth is accelerated by strong oxidizing conditions or heating in air. Too much heat can embrittle it. (over 600F) To answer your question you do not have to worry much about the Titanium. Just make sure it is clean and dry.

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Passivation/Pickling of Titanium

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