Double-pulse cyanide-free alkali silver electroplating method

Abstract

The invention discloses components of double-pulse cyanide-free acidic silver electroplating solution and a process. Silver nitrate is used as a main salt, sodium thiosulfate and ammonium thiosulfate are used as complexing agents, sodium metabisulfite is used as an auxiliary complexing agent, sodium sulfate is used as a conductive salt, boric acid is used as a pH value adjustor, and gelatin is added into the plating solution. The operation conditions comprise that the pH value of the plating solution is 4.0 to 4.5, the temperature of the plating solution is 20 to 30 DEG C, and the mechanical stirring speed is 100 to 150rpm. A silver plating layer with fine and compact crystallization can be obtained by adopting double-pulse electroplating, controlling the duty ratio, average current density and working time of the positive and negative pulses and electroplating on pure copper or copper alloy without silver immersion plating pretreatment. The plating solution of the invention has the advantages of simple formulation, easy control, strong even plating and covering capabilities, and high batch production stability. The plating layer has fine and compact crystallization and good appearance luster, and has no peeling, shedding and stripping; and the technology can replace a cyanide silver electroplating process, and can be used as a surface electroplating process for jewelries, artware and parts of electronic products.

Description

technical field [0001] The invention relates to the field of electroplating technology, in particular to cyanide-free electroplating silver technology and pulse electroplating technology. Background technique [0002] According to the different types of complexing agents, silver plating can be divided into two categories: silver plating with cyanide and silver plating without cyanide. Cyanide silver plating uses cyanide as a complexing agent, which is characterized by simple formula, good stability of plating solution and high quality of plating. It is often used for surface silver plating of small-scale, small-batch and other special parts. However, cyanide plating solution is highly toxic, difficult to treat waste water and waste liquid, serious environmental pollution, and seriously endangering the health of operators, so its application has been greatly restricted. The cyanide-free electroplating solution uses an organic complexing agent or an inorganic complexing agen...

AI Technical Summary

Problems solved by technology

However, the toxicity of cyanide plating solution is high, the treatment of waste water and waste liquid is difficult, the environment is seriously polluted, and it will seriously endanger the health of operators, so the application has been greatly restricted.

The cyanide-free electroplating solution uses an organic complexing agent or an inorganic complexing agent to replace the cyanide ion to complex the silver ion in the plating solution, so that it has the electrodeposition characteristics similar to the cyanide complexing agent when it is reduced, representative The system includes nicotinic acid silver plating process, ammonium iminodisulfonate silver plating, potassium ferrocyanide silver plating and sulfosalicylic acid silver plating system, etc. Problems such as poor performance and high production cost have not been well resolved, and have not completely replaced cyanide silver plating for mass production

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