Effects of o-vanillin as a brightener on zinc electrodeposition at iron electrodes

Effects of o-vanillin on electrodeposition of zinc on iron electrodes have been studied employing transient electrochemical, electrochemical quartz crystal microbalance, spectroelectrochemical, and surface analytical techniques. The results indicate that o-vanillin is adsorbed strongly on the iron surface, raising overpotentials for hydrogen evolution as well as for zinc deposition. o-Vanillin shows greater effects on the earlier stage of the zinc electrodeposition in the underpotential region than in the bulk deposition region. The additive appears to adsorb preferentially on the top of the dendritic growth sites, leading to a leveling effect. The zinc layer obtained in the presence of o-vanillin shows smoother morphology with smaller grain sizes and higher specular reflectance signals. Reflectance spectroelectrochemistry has been used for the first time to monitor the brightness of the electroplated surface. (C) 2004 The Electrochemical Society.