Plasma electrolytic oxidation is a novel improved anodizing method for surface engineering of light alloys specially aluminum alloys. There are several parameters affecting the coating quality and properties. This study investigated effects of the most two important parameters i.e., the current waveform and sodium tungstate additive on the Al 2 O 3 /TiO 2 plasma electrolytic oxidation nano-composite coatings. The evaluations showed that the nano-particles incorporated efficiently in the coating formation. X-Ray diffraction patterns showed that the nano-particles are inertly incorporated into the coatings. However, phase structure of the coating remained unchanged by the nano-particles incorporation. Although the zeta-potential of TiO 2 nano-particles is minus, changing the waveform from unipolar to bipolar and also increasing the cathodic duty cycle of the waveform changed neither the embedded content nor the uniformity of the nano-particles distributions on surface and cross-section of the coatings. The examination of SEM images of surface and cross-section of the coatings revealed that the morphology of the coatings is severely dependent on the applied waveform. Increasing the cathodic duty cycle of the waveform altered the morphology from pancake to crater and the addition of nano-particles and sodium tungstate did not affect this alteration. More thickness, roughness, compactness (less porosity) and hence the more corrosion resistance were achieved by using the waveform with wider cathodic duty cycle. The simultaneous incorporation of nano-particles and using uni-polar waveform decreased the thickness, increased the micro-cracks and widened the micro-pores. The short-term corrosion resistance of composite coatings produced by bi-polar waveforms were found lower than the simple coatings, but their long-term corrosion resistance was enhanced through “repairing mechanism”. The results revealed that the pore-plugging in the inner compact layer which is the main mechanism of repairing is more effective for the coatings produced by the waveform with wider cathodic duty cycle. Thus, the coatings with more intrinsic resistance benefits more from repairing mechanism. Voltage-time response graphs did not represent any difference by adding nano-particles to the electrolyte and in contrary, the voltage of all steps decreased by adding sodium tungstate additive. However, in contrast to nano-particles, by increasing the cathodic duty cycle of the waveform, the incorporation of tungstate anions, and hence, the tungsten content in the coating was decreased. Therefore, it was suggested that the incorporation of nano-particles is mechanical trapping enhanced electrophoretic while the incorporation of tungstate anions is just through electrostatic forces. The sodium tungstate additive led to create “pore band” when using uni-polar waveform which severely decreased the corrosion resistance. By using bi-polar waveform, the “pore band” was eliminated and the porosity decreased as well. The results showed that the tungsten-containing PEO coatings which are produced by bipolar waveforms benefit from repairing mechanism. The wear test results showed that decreasing the porosity and increasing the roughness contradict each other in a way that the wear resistance of the coatings remains unchanged. The nano-particles were found beneficial when the bipolar waveform with 20% cathodic duty cycle was applied while they were found detrimental for wear behavior of the coatings formed by unipolar and bipolar waveform with 40% cathodic duty cycle. It was found that the wear behavior of the PEO coatings are determined by load bearing capacity or coefficient of friction. The former is dependent on the thickness and porosity of the coatings while the latter is dependent on vertical load on ball, morphology and roughness of the coatings. The results showed that in contrast to the corrosion behavior of the coatings, the craters were essentially effective in wear behavior. The coatings produced by unipolar waveform have low load bearing capacity because of the low thickness and high porosity, thus, they showed low wear resistance. However, the wear mechanisms of the coatings produced by bipolar waveforms could be abrasion wear or brittle fracture. The results showed that the variation in chemical composition of the coatings arising from additives or waveforms did not play a significant role in wear behavior. Keywords: Plasma electrolytic oxidation; Aluminum; Coating; Alumina; Titania, Additive, Sodium tungstate, Corrosion, Wear