Texture and surface morphology in zinc electrodeposits

The texture and morphology of zinc coatings electrodeposited on low carbon steel substrate have been studied. The predominant texture component of zinc coating at low overpotentials was pyramidal (11.5) and (11.6) non-fiber while at high overpotentials (00.2) fiber component dominated. The morphological analysis of the coating surface indicates that the non-fiber texture component results from epitaxial growth of zinc which develops through 2D nucleation and bunching growth of substrate surface microsteps, while the (00.2) fiber component starts from 3D nucleation and oriented growth to promote the plane having the lowest surface energy (i.e., (00.2)) parallel to the steel substrate surface. Zinc hydroxide adsorption prevents 3D nucleation at low overpotentials and this process favors epitaxial growth of the zinc deposit. At high overpotentials, inhibited zinc adsorption, in addition to increased number of active nucleation sites, promotes strong (00.2) fiber component. Such variation in texture indicates that the electrodeposit texture is strongly dependant on overpotential.