Paper Title
THE EFFECT OF ANODIZING CURRENT DENSITY AND TEMPERATURE ON THE CORROSION RESISTANCE OF AAO/Ni-Ag INTEGRATED COATING ON AA5052 SURFACE FOR BIPOLAR PLATEAPPLICATION

Abstract
Bipolar plate plays a vital role in the Proton Exchange Membrane Fuel Cell (PEMFC) system, whichaccounts for 60–80% of the weight and 30–40 % of the total cost of a PEMFC stack. In recent years, there has been a growing interest in exploring aluminum alloys forbipolar plates. This is because the weight of an aluminum bipolar plate is 65% less than that of stainless steel, the most common metal bipolar plate used today. The only crucial challenge for aluminum bipolar plates is their inferior corrosion resistance in the acid environment of PEMFC. Therefore, surface modification on aluminum should be done to enhance its corrosion resistance. In this study, AA5052 plates were coated with AAO and Ni-Ag, respectively in order to be used as bipolar plates of PEMFC. The fabrication of AAO on the AA5052 surface was carried out by anodizing process in 16% H2SO4 at 25, 0, and -25oC with the current densities of 10and 20 A/dm2 for 30 minutes. The electrodeposition of Ni-Ag on anodized AA5052 was conducted in a solution containing 240 g/L NiSO4⋅6H2O and 7.5 g/L AgNO3 with the current density of 2 A/dm2 at room temperature for 15 minutes.The corrosion behavior of the integrated coating was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5M H2SO4 + 2 ppm HF at room temperature.The results indicated that the integrated coating on AA5052 substrates significantly increased the corrosion resistance of bipolar plates in the operating environment of a fuel cell when compared to uncoated substrates.The substrate coated under the anodizing current density of 20 A/dm2 and temperature of -25oC demonstrated the greatest performance: its corrosion rate was 57 times lower than that of an uncoated substrate, and theNyquistCurves showed the largest curve andhighest impedance value. Keywords - Bipolar Plate, PEMFC, Anodizing, Ni-Ag Electrodeposition, Corrosion Resistance