Formation and Cathodic Reduction of Taurine Complexes with Zinc and Cobalt(II)

Abstract

Stability constants of zinc and cobalt(II) complexes with Taurine were determined at 25°C and ionic strengths of 0.5, 1.0, and 1.5 (KNO₃). The thermodynamic stability constants were calculated. The processes in which zinc-cobalt alloys are electrodeposited onto 08kp steel from electrolytes with addition of Taurine and the physicochemical properties of the coatings were examined. It was shown that the ratio between the alloy components affect the chemical composition and microstructure of the coatings. The most homogeneous and finely crystalline structure is observed for zinc-cobalt alloy coatings obtained at a cathode current density of 1 A dm⁻² from an electrolyte with zinc concentration twice that of cobalt. At these concentration conditions, zinc-cobalt alloy coatings with 15.1 at % Co were obtained. The kinetic patterns of deposition of zinc-cobalt alloys at temperatures of 25 and 50°C were demonstrated. A relationship between the chemical composition, microstructure, and corrosion rate of the zinc-cobalt coatings obtained was determined.