Effect of Amphoteric Sn（IV） and In（III） Ions Added in an Alkaline Zincate Bath on Zinc Electrocrystallization

Zinc deposits in an alkaline zincate bath were investigated using scanning electron microscopy and X-ray diffraction analysis. Zinc deposits obtained from an alkaline zincate bath were electrocrystallized under －0.5 A/dm2, 30 min at 25℃, which always showed the usual spongy or dendritic structure. In cases where the amphoteric Sn（IV）ion was added to zincate bath, the dendritic structure was shown. However, the amphoteric In（III）ion was added to the bath, which produced deposits comparable to the block-like structure. Both the amphoteric Sn（IV）ion and In（III）ion were added to the bath, which also produced deposits comparable to the block-like structure. Effects of the In（III）ion were especially evident on zinc crystallization, which caused the preferred orientation with the ｛10·2｝ and ｛10·3｝ planes of zinc deposits. These phenomena occurred by differences in the effects of cemented Sn or In on zinc deposition.