The invention relates to the technical field of
cyanide-free silver plating solutions and preparation, and discloses a
cyanide-free silver plating solution based on composite coordination and double-pulse fine regulation and a preparation method thereof.The
cyanide-free silver plating solution comprises silver salt, a composite coordination agent,
supporting electrolyte, a pH
regulator and a composite functional additive, the silver salt provides silver ions with the concentration being 15-50 g / L, and the composite coordination agent provides silver ions with the concentration being 15-50 g / L; the composite coordination agent is composed of 80-140 g / L of a
hydantoin main coordination agent and 15-30 g / L of a
nitrogen heterocyclic
amide auxiliary coordination agent, the concentration of the
supporting electrolyte is 75-130 g / L, the
supporting electrolyte is used for enhancing the
conductivity of the plating solution, and the pH
regulator is used for maintaining the pH value of the plating solution within the alkaline range of 9.0-11.5; the composite functional additive comprises 0.5-4 g / L of a main brightener, 0.1-1.5 g / L of an auxiliary brightener and 5-25 g / L of a grain refiner, and is used for improving the glossiness and compactness of a plating layer; through the preparation method, the difficulty and cost of
wastewater treatment during solution plating can be reduced, the
environmental protection effect is improved, and the stability of the plating solution during long-term use is improved.