Electrode kinetics connected to deposit growth for zinc electrodeposition: Influence of surfactants
Abstract
Impedance measurements and SEM examination of deposits show that the mechanism of zinc deposition in zincate alkaline electrolytes is highly sensitive to the electrolyte content in anodically dissolved zinc (ADZ). Two distinct electrode kinetics closely connected to the deposit growth are pointed out: (i) a low-frequency capacitive feature when spongy deposits are formed in the presence of ADZ and (ii) a low-frequency inductive feature for the formation of granular deposits. This correlation subsists in the presence of surfactants which inhibit the growth of zinc moss and dendrites: then the impedance plots are typical of the mechanism leading to granular deposits with various roughness and grain size. By changing the rates of interfacial reactions, the surfactants yield an increased charge transfer resistance. A fluorinated surfactant generates a stronger inhibiting effect which strengthens with increasing concentration of ADZ.