Effect of Pulsed Current Frequency on Morphology and Corrosion Behavior of Plasma Electrolytic Oxidation on Aluminum

Protective oxide coatings are developed on aluminum substrate through plasma electrolytic oxidation using a pulsed current and within the alkaline electrolyte. The morphology and corrosion resistance of the oxide layer established under a pulsed current condition have been previously carried out. Since the frequency is one of the main characteristics of the pulse current, the results were performed to investigate the effect of this factor. As the results specified, by increasing the pulse frequency, power of each pulse is individually reduced; therefore the required strength to break the dual capacitive layer on the sample surface is reduced. As a result, ignition is initiated at a higher voltage. The results show that with increasing time at a frequency of 10 000 Hz and duty cycle of 25% the thickness was increased exponentially. It is also revealed that applying pulses with a higher frequency, can improve corrosion resistance significantly.