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Compatibility of SS904L with nitric Acid

2003

We are trying to help one of our customers find a solution for a flow measurement application. Currently a flow meter using Titanium sensing tubes are used. The application will see up to 10-12%Nitric acid at 180 °F during cleaning cycles.

The Titanium tubes shows signs of severe cracking and corrosion after about 6 months. We are looking at using SS904L as an alternative but have been unable to find conclusive data that the SS904 will be a long lasting solution. All other piping is SS316L and shows no sign of corrosion.

Any help based on previous experience or directions where supportive data can be found is greatly appreciated.

Ola

Ola Wesstrom
instrumentation supplier - Greenwood, Indiana, USA

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I have no data on 904L in this environment, but would think that it will be good if the 316L is working.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2003

Lee is correct, Type 904L stainless steel should perform well under these conditions. Nitric acid is a strong oxidizer, so this means that the passive film on stainless alloys remains intact. Only when the temperature or concentration are much higher will corrosion be a concern. Titanium usually performs well in nitric acid environments, but above 80 °C there is a strong dependence on the purity of the acid.

Toby Padfield
- Michigan
2003