Research Progress on Cyanide-Free Silver Plating Additives

The development of environmentally benign, cyanide-free silver electroplating technologies to produce high-quality deposits and replace highly toxic cyanide-based processes is a major research focus in the field. Additives play a vital role in controlling electrodeposition behavior and coating properties. To optimize both bath performance and coating characteristics, research on additives has progressed from studying single-component mechanisms to the systematic design of composite additive systems based on theoretical and experimental foundations. These developments have enabled cyanide-free silver plating not only to match but also to exceed traditional cyanide-based processes in key performance metrics, such as brightness, leveling ability, and adhesion. However, in industrial applications, cyanide-free systems continue to encounter substantial engineering challenges, including the long-term stability of plating solutions, the need for viable operational windows across a wide range of current densities, and the comprehensive costs associated with wastewater treatment. This review systematically summarizes recent advances in cyanide-free silver plating, with a focus on the mechanisms, classification, and research trends of additives. Current challenges in practical applications are also discussed, aiming to provide a theoretical basis and strategic guidance for the development of high-performance, environmentally friendly multifunctional additives.