System linearity quantification for in-situ impedance spectroscopy of plasma electrolytic oxidation

A frequency-swept pulsed voltage signal approximating an implied single-sine perturbation and its current response were analysed in the frequency domain to evaluate system linearity and instantaneous impedance of the PEO process. For selected process parameters, the noise and nonlinearity distortions were found to be ≤ 15%, indicating that the studied PEO system can be considered as a properly linearised object.

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► New method to quantify linearity of an electrochemical system proposed
► Linear R1(R2C) circuit and PEO system operated in large signal mode considered
► Instantaneous impedance values obtained in 20 Hz–20 kHz range for 0.5 s sweep
► It is shown that pulsed bipolar PEO processes can be linearised to R^2 ≥ 0.85.
► EIS modelling of PEO processes is enabled.