Effects of some additives on the corrosion behaviour and preferred orientations of zinc obtained by continuous current deposition

The effect of thiourea, urea and guanidin on zinc deposits obtained from chloride baths under continuous current conditions are described and discussed. The corrosion behaviour of the deposits was investigated in an aerated 3.5% NaCl solution; anodic polarization curves, polarization resistance (R _p) measurements and weight-loss studies were performed. The corrosion resistance of zinc deposits improved in the presence of urea. The deposit morphology was analyzed using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) was used to determine the preferred crystallographic orientations of the deposits. The preferred crystallographic orientations of zinc deposits (112) do not change in the presence of urea and guanidin except for an increase in the peak intensity of the (112) plane. In the presence of thiourea, zinc deposits crystallise in two textures; (100) and (110). The influence of each additive and the difference between additives on the zinc deposits are also discussed.