Characterization of ceramic oxide coatings prepared by plasma electrolytic oxidation using pulsed direct current with different duty ratio and frequency

•The frequency and duty ratio had a considerable influence on the coating properties of Al 5083-O in DC power mode.•The PEO coating layer was comprised of Al-based, Mg-based and Si-based oxides, regardless of the applied pulse conditions.•Thickness of the PEO coating tended to increase with decreasing duty ratio at the same frequency.•The PEO coating improved the corrosion resistance of Al 5083-O from a minimum of three times to a maximum of one order. In this study, plasma electrolytic oxidation (PEO) was performed on the commercial aluminum 5083-O alloy using pulsed direct current (DC) power source. The coating process was carried out in KOH 2 g/L + Na2SiO3 2 g/L electrolyte with the systematic change of frequency (100–2000 Hz) and duty ratio (20–80%). The coating was characterized by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), and potentiodynamic polarization experiment. The coating layers showed different growth behavior and chemical composition by frequency and duty ratio. The PEO coating improved the corrosion resistance of Al 5083-O from a minimum of three times to a maximum of one order. In conclusion, it was found that the frequency and duty ratio had a considerable influence on the coating properties of Al 5083-O in DC power mode.