Effect of Thioglycolic Acid on Zn Electrodeposition on the Steel Sheets

Abstract

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.