CHARACTERIZATION CORROSION BEHAVIOR OF NANO ALUMINA COATINGS ON Al12Si FABRICATED BY ELECTROPHORETIC DEPOSITION

Abstract

This paper compares the corrosion behavior of Al2O3 coatings produced by Electrophoretic technique to Nano-sized alumina coatings on aluminum alloy surfaces by using a well dispersed stable suspension produced by addition of Al2O3 powder plus a small amount of water and iodine to ethanol. Electrophoretic deposition for (2,3,4 and 5) min at (50-60) V resulted in formation of a uniformly dense film on the top, The maximum defect-free sintered thickness by EPD allowed us to obtain coatings as thick as 7 µm. The protective behavior against corrosion and the corrosion kinetics of the produced films were studied through polarization resistance (PR) measurements in aggressive media (sea water). The corrosion resistance with sintering to 400C° with 2hours holding time has decreased the corrosion current density (about 32μAcm2) when compared coatings without sintering for coatings produced by EPD. Moreover, alumina coatings present an excellent resistance in sea water. AFM observations suggest that coatings produced by EPD are homogeneous and defect-free. The aim of this work has been to prepare thick Al2O3 coatings deposited by EPD in order to increase the corrosion resistance of aluminum substrates. The corrosion resistance of the coatings has been evaluated through electrochemical methods as a function of different processing parameters: final thickness of the coating, applied voltage, and deposition time.