Abstract:Cyanide-free sulfite electrodeposited gold system has the disadvantages of low current efficiency, poor stability of plating bath, short cycle period. To improve the current efficiency, the stability of the plating bath and the surface gloss of the coating, the electrodeposited gold morphology and the performance of the coating are improved. In this paper, sodium gold sulfite electroplating solution was prepared with different concentrations of ethylenediamine (EDA) as additives. The effects of EDA on the stability of plating solution, surface morphology, element composition and crystal orientation of electrodeposited products, and gloss, hardness and roughness of gold coating were studied. The effect of EDA on Au(I) behavior in solution was further studied by electrochemical testing. The results show that EDA increases the active site of Au+ adsorption by 2.8 times, increases the polarization of cathode surface, promotes grain refinement, and enhances the peak strength of Au(111) crystal surface. When the EDA concentration is 15 g/L, the electroplating solution can be stored for more than 6 months, the current efficiency increases from 54% to 98%, the surface uniformity, gloss and hardness of the gold coating are significantly improved, the surface roughness and corrosion rate of the coating are significantly reduced, and the comprehensive performance of the coating is the best. The research results are expected to provide reference for the development of new high-efficiency additives for sulfite plating system, and help promote the sustainable development of gold electroplating industry.