Electrochemical characteristics of ZrNi4.8M0.2 alloys in strong alkaline solution

The effect of partial substitution of Ni with Sb, Bi or Al + Li in ZrNi5 compound on hydrogen absorption has been investigated using the electrochemical method of hydrogen desorption rate. The samples were cathodically charged in 6 M KOH solution. The electrochemical charging and discharging experiments have shown that the ZrNi4.8Bi0.2 alloy is capable to absorb the highest quantities of hydrogen. Potentiokinetic polarization curves in strong alkaline solution have been measured for the series of ZrNi4.8M0.2 (where M = Sb, Bi or Al + Li) alloys. It is shown that the presence of Bi in the hydrogenated alloy causes distinct increase of anodic current in passive range and thus worsens the passivating properties of the alloy. Polarization resistance of the tested alloys measured at potentials close to equilibrium potential of H2O/H2 system allowed to evaluate exchange current densities for hydrogen absorption–desorption process.