The object of this work is to synthesize alumina coatings by plasma electrolytic oxidation (PEO) on 6061-T6 Al alloys. Electrolytes (0.1M NaAlO2) with small amounts of KMnO4 ranging form 0.8 to 3.0 mM were employed during PEO at a constant current density of 10 A/dm2. With the added KMnO4 of 0.8-3.0 mM, the onset of spark discharge was delayed. The coatings revealed yellow color. X-ray diffraction results showed the obtained coatings consisted mainly of α-Al2O3 and γ-Al2O3 phases. As the concentration of the added KMnO4 was raised to above 0.8 mM, the thickness and roughness of the coatings increased rapidly with time. The coatings prepared by PEO with 0.8 mM added KMnO4 for 60 minute reached 51 μm and exhibited excellent corrosion resistance in terms of potential, as well as impedance. The coatings may be applied to corrosion protection applications.