Zinc electrodeposition from alkaline zincate solution by pulsating overpotentials

It is well known that smooth zinc deposits cannot be obtained from alkaline zincate using constant overpotential and current rate. During prolonged metal deposition, spongy and dendritic deposits are formed. It has been shown that the deposits are less agglomerated in the case of square-wave pulsating overpotentials regime than the ones obtained in case of constant overpotential regime. This is explained in a semiquantitative way by two phenomena: selective anodic dissolution during overpotentials off period and decreasing diffusion control. These effects is more pronounced at higher pause-to-pulse ratio. Increasing the pause-to-pulse ratio causes a reduction of the ratio between diffusion and activation overpotential, resulting in a more compact deposit. Confirmation of the proposed semiquantitative mathematical model was obtained by zinc electrodeposition onto a copper wire from a 0.1 M zincate solution in 1.0 M KOH at room temperature.