Influence of voltage waveform on anodic film of AZ91 Mg alloy via plasma electrolytic oxidation: Microstructural characteristics and electrochemical responses

• Published in: Journal of alloys and compounds Vol. 586; pp. S357 - S361
• Main Authors: Ko, Young Gun, Lee, Eung Seok, Shin, Dong Hyuk
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier B.V 15.02.2014; Elsevier
• Subjects: Anodic; Anodic film; Asymmetry; Corrosion; Electric potential; Magnesium base alloys; Mg alloy; Microstructure; Plasma electrolytic oxidation; Scanning electron microscopy; Voltage; Waveform; Waveforms; Waveform; Anodic film; Mg alloy; Corrosion; Plasma electrolytic oxidation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.03.015

•The effect of voltage waveform on the anodic film structure is significant.•The anodic film by asymmetric-sine wave is denser than that by half-sine wave.•Asymmetric-sine wave results in excellent electrochemical properties. The present study investigated how the voltage waveform influenced the microstructural characteristics and electrochemical responses of the anodic film on AZ91Mg alloy coated by plasma electrolytic oxidation (PEO). PEO coatings of AZ91Mg alloy were performed for 600s in an alkaline silicate electrolyte with respect to the voltage waveform such as half-sine and asymmetric-sine waveforms. Microstructural observations on cross section of the anodic film utilizing scanning electron microscope revealed that the anodic film formed via asymmetric-sine wave was much denser in structure than that via half-sine counterpart since the occurrence of the cathodic breakdown between the anodic pulses could effectively suppress the formation of the micro-pores and discharge channels in the anodic films. Thereby, the hardness and corrosion properties of the anodic film formed by asymmetric-sine wave were found to be superior to those by half-sine wave. In addition, electrochemical responses were interpreted in relation to the equivalent circuit model consisting of resistor and capacitor elements within an electrical cell.