This study investigated effects of thioglycolic acid on Zn electrodeposition behavior in sulfate baths. Polarization curves revealed that addition of thioglycolic acid to the bath increased the critical current density for Zn deposition and decreased the overvoltage for Zn deposition. Regarding the deposited Zn, the addition of thioglycolic acid increased the crystal orientation index of （0002） Zn and decreased the deposited Zn particle size. From polarization curves using baths not containing Zn ions, the hydrogen reduction reaction was found to be accelerated by the addition of thioglycolic acid. Presumably, the critical current density for Zn deposition was increased by preventing an increase in the overvoltage of the hydrogen reduction reaction by adding thioglycolic acid. The increase in the orientation index of （0002） Zn caused by adding thioglycolic acid can be attributed to a decrease in the overvoltage for Zn deposition.
Nickel（Ni）-tin（Sn）layers were electroless-deposited on iron（Fe）substrates from baths containing nickel sulfate（NiSO4）, sodium citrate（Na3C6H5O7）, and sodium stannate（Na2SnO3）with sodium hypophosphite（NaH2PO2）and dimethylamine-borane（C2H7N･BH3）as reducing agents. By optimizing the bath composition, 0.4-0.8-μm-thick Ni-Sn layers with atomic Sn content of 40-50% were formed on the Fe substrates during 20-min deposition. The Sn content in Ni-Sn layers achieved in this study is the highest ever reported. Analyses by X-ray photoelectron spectroscopy（XPS）and X-ray diffractometry（XRD）confirmed uniform dispersion of Ni and Sn atoms in the layer and indicated the Ni-Sn layers as the main structures of Ni1.5Sn. A bath prepared with a C2H7N･BH3 reducing agent exhibited durability for Ni-Sn layer electrodeposition persisting up to eight times as long as that prepared using NaH2PO2. Chemical resistance property tests indicated that Ni-Sn layers prepared with NaH2PO2 had high resistance against 25 wt.% hydrogen peroxide（H2O2）aqueous solution. No dissolution of the Ni-Sn layer or Fe substrate was observed for 72 h.