Plasma electrolytic oxidation (PEO) is a Novel method of surface treatment which in-situ forms ceramic coatings on the surface of light metals like Al alloys under plasma conditions and improves the properties like hardness and corrosion resistance of the surface. The characteristics of PEO coatings can be influenced by two main factors: the applied current regime and the electrolyte composition. In this study, PEO coatings on 7075 Al alloy were prepared in both simple silicate based electrolyte and at the presence of KMnO 4 additive varying from 0.5 to 3 g/L. the results showed for the coating produced in the base electrolyte, crystalline g-Al 2 O 3 was the main phase, while the coatings formed in the presence of KMnO 4 consisted of a-Mn 2 O 3 . A pancake structure was observed on surface of the coating produced in the base electrolyte, while in the presence of KMnO 4 , the structure has been changed and a foam feature was detected on the surface of the coatings. The KMnO 4 changed the discharge types leading to diminish the large pores and caused compacter structure, so the coating produced in 3 g L -1 KMnO 4 solution showed superior corrosion performance. The research was continued by examining the other main factor i.e current regime. Therefore, this work showed that by applying bipolar current mode and controlling cathodic pulse time, the strong plasma discharges with high temperature spikes could be eliminated and hence the quality of the coatings was considerably improved. The coating formed at bipolar regime with a longer cathodic pulse time due to its compactness and thickness showed better corrosion and mechanical properties than PEO coatings formed at unipolar current regime.