Role of additives in bright zinc deposition from cyanide free alkaline baths

A new additive formulation for non-cyanide alkaline zinc baths was identified after experiments with various additives. Polyvinyl alcohol addition was found to be the best primary additive of those tested. The secondary additives selected belonged to the aldehyde group. The selection of the additives was made based on Hull cell, cathode current efficiency and throwing power studies. Thickness measurements at various points on a cathode indicated uniform thickness distribution. XRF showed uniform deposition. SEM examination indicated a fine-grained deposit structure. Finally, the influence of each additive was studied using cyclic voltammetry.