Effects of Pd substitution for Ni on corrosion performances of Mg0.9 Ti0.1Ni1-xPdx hydrogen storage alloys

The Mg0.9 Ti0.1Ni1-xPdx (x= 0, 0.05, 0.1, 0.15) hydrogen storage electrode alloys were prepared by mechanical alloying. The main phases of the alloys were determined as amorphous by X-ray diffraction(XRD). The corrosion potentials of the alloys were measured by open circuit potential measurements and the values are −0.478, −0.473, −0.473 and −0.471 V (vs Hg/HgO electrode) for x=0, 0.05, 0.1, 0.15, respectively. The corrosion currents of the studied alloys were obtained by non-linear fitting of the anodic polarization curve using Bulter-Volmer equation and Levenberg-Marquardt algorithm, which were obtained after different cycles. The initial corrosion currents of the alloys are decreased with the increasing of Pd content. The increasing of Pd content in the alloys inhibits the corrosion rates of the electrode alloys with the progress of cycle number. The electrochemical impedance spectroscopy(EIS) was conducted after open circuit potential of the alloys stabilizing. The impedance data fit well with the theoretical values obtained by the proposed equivalent circuit model. The corrosion resistances and the thickness of surface passive film of the alloys, which were deduced by the analyses of EIS, are enhanced with the increasing of Pd content in the alloys, which are consistent with the results of corrosion rates obtained from anodic polarization measurements.