Nitric Acid Pump Impeller Corrosion
JohnH asked on
Hi,
We are pumping nitric acid right now using a Hastelloy C276 impeller that is getting eaten up pretty quickly. We believe we are having not only corrosion issues but some cavitation due to the corrosion pattern. Any suggestions or info on if Ultramet CPT's tantalum will help with this issue?
gambale replied on
Hello John
Good question. As far as tantalum's corrosion resistance to nitric acid there is really nothing better. Tantalum will certainly perform better than Hastelloy C276 in your environment.
The area you need to be careful about is the cavitation. Pump impeller cavitation could be very erosive depending on how severe the issue is. The result is it causes erosion corrosion. This is a process where the protective oxide surface is eroded away and then the base metal is free to corrode. As this happens pits are developed and the pumping efficiency goes down.
In the case of tantalum Ultra-Metal surface, tantalum is extremely resistant to erosion corrosion due to tenacious oxide layer but it could be compromised if the cavitation is severe enough.
What I would recommend is to first solve your cavitation issue via impeller design as best you can, then improve the materials as needed for you corrosive application.