SYMPOSIA PAPER Published: 01 January 2001

Characterization of Organic Surfactants and Dispersants by Frequency-Dependent Dielectric Thermal Analysis and Electrochemistry


Multi frequency electrochemical impedance spectroscopy (EIS), dielectric thermal analysis (DETA), and cyclic voltammetry (CV) were employed as a basis for evaluating organic detergents and dispersants in a hydrocarbon based lubricating oil. These dielectric and electrochemical techniques appear to be a powerful tool capable of detection and monitoring of oil additives, surfactants and dispersants, and investigation of general mechanisms of oil degradation in an operating engine. These techniques were applied to the identification and detection of various types of chemical additives.

Measurement of electrochemical impedance spectroscopy over a sufficiently wide range of frequencies, electrochemical potentials, and temperatures yielded detailed qualitative and quantitative information. EIS ceded the dynamics of charge transport and reduction or oxidation reactions of ionic species and individual chemical components across the bulk lubricant and at the electrode-lubricant interface. Highly selective studies of spatial distribution of charge-transfer processes taking place in bulk solution and at the interface were achieved. A combination of EIS and CV based electrochemical methods provided a complete chemical analysis of lubricant conditions. These included detection, quantification and differentiation of adsorption and lubricant film formation on an electrode surface, and investigating kinetics of reduction or oxidation reactions of major oil components (detergents, dispersants, etc.). DETA polarization plots clearly ranked the surface-active detergents and the less active dispersants. Frequency dependent EIS, and DETA, as well as CV can be easily used for characterizing chemical additives for engine oils.

Author Information

Lvovich, V
Lubrizol Corp., Wickliffe, OH
Cahoon, J
Cleveland State University and TechCon Inc., Cleveland, OH
Riga, A
Cleveland State University and TechCon Inc., Cleveland, OH
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Developed by Committee: E37
Pages: 157–173
DOI: 10.1520/STP10707S
ISBN-EB: 978-0-8031-5452-0
ISBN-13: 978-0-8031-2887-3