Abstract
On-line, real time corrosion monitoring in processes featuring low conductivity fluids akin to sulfolane aromatic extraction, have represented a challenge for traditional electrochemical techniques. Sulfolane specific conductance that is typically about 5μS/cm disables proper determination of corrosion current with standard Linear Polarization Resistance (LPR) technology. Other electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) or Zero Resistance Ammetry (ZRA) that are capable to measure corrosion in low conductive fluids are useful mostly in laboratory practice, but offer little or no utility for field application. Therefore, corrosion processes in sulfolane units are mostly monitored by time-lagging techniques like electrical resistance (ER) and corrosion coupons or by purely qualitative approaches utilizing sulfolane color as the “corrosivity indicator”.
The authors’ earlier work on multi-electrochemical, industrial corrosion monitoring technique integrating impedance measurement, Electrochemical Noise (ECN) and Harmonic Distortion Analysis showed demonstrable efficacy in fast and accurate determination of instantaneous corrosion rate in low-conductivity sulfolane solutions. Initial data showed that properly adjusted surface area of the electrode facilitates attainment of stable corrosion trends in sulfolane solutions at conductance of about 2-5 μS/cm. Rapid response of the sensor to process changes (temperature, oxygen, water), in both general and localized modes, was also observed.
The current paper provides additional data and insights from the authors’ continuing research on sulfolane corrosivity utilizing industrial-type corrosion sensors. Results from comprehensive evaluation of the impact of aqueous phase as well as other relevant process parameters on general and localized corrosion of ferrous metallurgy in sulfolane fluid are presented in this paper.
