Study of silicate and aluminate coatings obtained by plasma electrolytic oxidation of aluminum alloy

Aluminum alloys are used for various purposes and in the most of cases the surface of such materials needs to be modified in order to improve properties such as wear resistance and corrosion. In this scenario, plasma electrolytic oxidation (PEO) process comes up as a viable alternative for the production of coatings on these substrates, since aluminum has low melting point and this process occurs at low temperatures. In this work, coatings obtained by PEO were produced on the surface of aluminum alloys, using different parameters in order to compare the properties of produced coatings. The coatings obtained were characterized by electrochemical impedance spectroscopy (EIS) in order to analyze the performance against corrosion. Equivalent circuit model was used to adjust the EIS curves, with a view to better understand the behavior of coatings. From the obtained results it was possible to verify that at lower voltage (250 V), there was a greater formation of film on the substrate and consequently a better protection of the same. When compared to uncoated aluminum, the coated samples presented an improvement of corrosion resistance.