Effect of frequency on plasma electrolytic oxidation of zirconium in pulsed unipolar mode

Using the method of in situ impedance spectroscopy, an optimization of plasma electrolytic oxidation (PEO) was performed, and the influence of the pulse frequency was evaluated for the coating of Zr-1Nb alloy. It was shown that the in situ impedance modulus decreased with increasing the pulse frequency in a pulsed unipolar mode. Also, the protective properties of the coating improved with frequency; this was attributed to the increase in the uniform distribution of the microdischarges over the sample surface. As a result, the optimal frequency range of PEO was justified based on the impedance spectroscopy studies. (paper)