EFFECT OF PRIOR CATHODIC POLARIZATION ON THE ANODIC-DISSOLUTION OF NICKEL IN ACIDIC SOLUTIONS

A combination of electrochemical and radiometric methods was used to study the effect of hydrogen absorbed by nickel during prior cathodic polarization, on the metal's subsequent anodic behavior in 1 N H2SO4 solutions. It was shown that during the initial period of anodic dissolution of such an electrode, hydrogen is ionized preferentially while nickel dissolution is inhibited. The rate of nickel dissolution increases as the layer of nickel containing the absorbed hydrogen is etched away, and rises to values equal to the applied current, while the electrode's potential shifts in the negative direction and attains the values corresponding to dissolution of the original nickel under the same conditions. The inhibiting effect of hydrogen incorporated into nickel was explained in terms of blocking of nickel atoms in half-crystal positions on steps of the nickel lattice by adsorbed hydrogen atoms.