Evaluation of industrial cutting fluids using electrochemical impedance spectroscopy and multivariate data analysis

In this paper we explore the combination of electrochemical impedance spectroscopy (EIS) and multivariate data analysis to evaluate the concentration and pH of an industrial cutting fluid. These parameters are vital for the performance of for instance tooling processes, and an on-line quality monitoring system would in such applications be very beneficial. It is shown that both the total impedance and the phase angle contain information that allows the simultaneous discrimination of the concentration and the pH. The final evaluation was conducted using the regression technique partial least squares (PLS), and this approach provided a way to quickly and easily find the correlation between EIS data and the sought parameters. The possibility to estimate both the concentration and pH level clearly indicates the potential of this method to be implemented for on-line evaluation.