UREX+ centrifugal contactor corrosion in HNO3-HF aqueous solutions
The UREX+ is an advanced solvent extraction process under development to separate uranium from nuclear waste. This operation utilizes 304L stainless steel (SS) centrifugal contactors. The contactor is exposed to two different fluids that flow continuously; these are aqueous and organic solutions which are identified also as phases. These two solutions are ultimately separated at the end but during the process they form different mixtures at several regions under various hydrodynamic conditions. Our investigation focuses on the corrosion of the stainless steel in acidic aqueous solutions. The critical operational parameters considered in this study are the presence of different acids and temperatures. In this investigation 304L SS coupons were exposed to three types of corrosion tests that mimic the corrosion environments present in centrifugal contactor during its operation. The corrosion tests have been conducted in the following aqueous solutions: 5M HNO3; 5M HNO3 + 0.1M HF; and 5M HNO3 + 0.1M HF + 0.1M Zr4+. The three types of corrosion tests used were immersion tests, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). A rotating cylinder was used in a three-electrode cell configuration to obtain corrosion data based on potentiodynamic polarization and electrochemical impedance spectroscopy techniques in order to assess the performance of 304L stainless steel at different rotating rates. The corrosion tests were carried out at three temperatures (25, 40 and 80°C). The results showed that the mixture of HNO3-HF acids is the most corrosive environment tested and addition of Zr4+ ions reduce the damage caused by hydrofluoric acid by forming zirconium fluoride complexes. Also, the increase of temperatures leads to higher corrosion rates in all solutions used. © 2010 by NACE International.
author list (cited authors)
Jahangiri, N., Raraz, A. G., Indacochea, J. E., & McDeavitt, S. M.