THE VOLTAMMETRIC BEHAVIOR OF NICKEL IN SODIUM-HYDROXIDE SODIUM SULFIDE SOLUTIONS

Voltammograms of Ni in 0.01 M NaOH containing Na2S (3 x 10(-4) M < c(Na2S) < 10(-1) M) run from -1.06 up to 0.9 V(RHE) show a multiplicity of anodic peaks which are assigned to the initial formation of a NiS two-dimensional (2D) layer. the thickening of the NiS layer, the formation of a (NiS + S(x)) layer, and in 0.1 M Na2S + 0.01 M NaOH to the rupture of the anodic film accompanied by corrosion of Ni. The thickening of the NiS layer behaves as an irreversible reaction under diffusion control, and the formation of a (NiS + S(x)) layer obeys the kinetics of an electrode process under ohmic control. The anodic layers involved at different stages of the global reaction are discussed. Conjugated cathodic peaks related to the above reactions are also described.