In-situ estimate of coating by equivalent circuit for PEO of AZ31B

ABSTRACT

The paper discusses an in-situ estimated methodology of coating using the equivalent circuit for the plasma electrolytic oxidation (PEO) process. An equivalent circuit of the second-order nonlinear structure can be proposed from the transient load waveform and the arc image recorded during pulsed bipolar PEO treatment. The transfer function of the linear part of the model was derived from Kirchhoff's law and Laplace's transformation rule; the nonlinear part of the model was fitted using Fitting Theory. Then the calculation method of each element value was derived in the equivalent circuit. The characterisation results of the coating properties show that the changes of different element values by the equivalent circuit can reflect the changes in coating thickness, coating density and discharge intensity. The relationship between the values of several elements and the microstructure of the coating is analysed comprehensively; a prediction method for the corrosion resistance of the coating is provided.

KEYWORDS:

• AZ31B magnesium alloy
• plasma electrolytic oxidation (PEO)
• equivalent circuit model
• quantitative calculation
• in-situ estimate
• coating thinckness
• coating density
• corrosion resistance of coating

Acknowledgements

Upon completion of this paper, I would like to take this opportunity to express my sincere gratitude to my institution, Lanzhou University of Technology, for providing me with a good experimental environment. Thanks to Y.C Liu, H.M Liu, B. Li, Y. Ma and Y.F Lan for their dedication to research work. I am also obliged to Project (21JR7RA241) and Project (20YF8GA001) which have given me financial support. Last but not least, I would like to thank the editors and reviewers for taking the time to read my paper; it has been an honour to engage in scholarly exchange with you.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by The Innovation Base and Talent Program – Science and Technology Foundation of Gansu Province, China: [Project Number (21JR7RA241)]; The Key R&D Program of Gansu Province, China: [Project Number (20YF8GA001)].