Effects of four N-based additives on imitation gold plating

In this work, it investigated a non-cyanide imitation gold plating system, namely a hydroxyethylidene diphosphonic acid system. The bath in this system is less toxic and less expensive, and the decorative quality of the coating can be maintained with this system. The effects of four N-based additives, namely triethanolamine (TEA), ammonium fluoride (AF), ammonia triacetic acid (NTA), and polyacrylamide (PAM), on the performance of the Cu–Zn–Sn alloy coating were studied. The results indicate that TEA can be used as an auxiliary complexing agent to promote anodic dissolution, improve the dispersibility of the bath, and control the colour and brightness of the coating. The carboxylic acid group of NTA is easily discharged in the cathode, inducing the hydrogen evolution reaction, which results in a blackened and irregular coating surface. In addition to inorganic amines, AF also contains fluoride ions, which enable the formation of uniformly sized particles, dense crystals, and a compactly arranged coating, and may promote the formation of a yellow coating. The long chain of PAM prevents the migration of Cu2+ ions in the solution, which causes a decrease in the anodic stripping peak current and thus adversely affects the electrode interface. The mechanism of the four additives in the electroplating process was studied, and the results may provide theoretical guidance for selecting additives for the Cu–Zn–Sn electroplating process.