CN101665963A - Environmental non-cyanide plating solution for silver-plating - Google Patents

Abstract

An environment-friendly cyanide-free silver electroplating solution without cyanide. The plating solution contains silver ion sources, complexing agent amino acid compounds and derivatives thereof, auxiliary complexing agents and electroplating additives. The composition ratio and process conditions are: silver salt 0.01~1mol/L, amino acid compound or its derivatives 0.01~10mol/L, auxiliary complexing agent 0.002~2mol/L, electroplating additive 0.001~2.0g/L, silver plating The pH of the solution is 6-14, and the temperature of the silver-plating solution is 10-70°C. Compared with the traditional formula of silver plating with cyanide, this environmentally friendly silver plating solution has the characteristics of clean electroplating; at the same time, the replacement rate of silver ions in the plating solution with active metals and alloy substrates such as copper and copper alloys is very slow, and silver plating One-step electroplating method can be used in the process, without pre-plating silver or immersion silver, and the coating is bright and has good bonding force.

Description

An environment-friendly cyanide-free silver electroplating solution

technical field

The invention relates to the technical field of electrochemical silver plating, in particular to a formula for an environment-friendly cyanide-free silver plating solution used to replace highly toxic cyanide silver plating solution

technical background

Silver plating has been widely used in fields such as decorations, tableware and electronic products. So far, most of the electroplating silver processes at home and abroad still use the cyanide silver plating process to electroplate the silver layer. However, cyanide is highly toxic and extremely harmful to humans and the environment. With the strengthening of environmental protection awareness and the promulgation of relevant policies in various countries around the world, cyanide electroplating has become a process with restricted declarations and eliminated in principle.

Compared with the cyanide silver plating process, the research on the cyanide-free silver plating process has been done in recent decades. Cyanide-free silver plating uses inorganic or organic compounds to replace cyanide as a complexing agent for silver ions, so as to increase the cathodic polarization of the plating solution, so that the silver can be reduced to have electrodeposition characteristics similar to cyanide complexing agents. So far, although electroplating workers at home and abroad have conducted a lot of research on cyanide-free silver plating, none of them can completely replace cyanide silver plating. There are roughly the following problems: (1) the silver-plated layer is easy to change color. Silver has good chemical stability in most organic acids, strong acids and salt solutions, but in the air containing halides and sulfides, the surface of silver will change color quickly. This is a common problem in all silver plating (including cyanide silver plating process), so post-plating treatment is generally required. (2) The bonding force of the coating is poor. Silver-plated parts are generally copper and copper alloys. Since the standard potential of copper is much more negative than that of silver, when copper and its alloy parts enter the plating solution, a replacement reaction occurs before power is applied, and a replacement layer is formed on the surface. The bonding force is poor, and some copper impurities contaminate the plating solution. Pre-plating silver is often used to avoid such problems. (3) The stability of the plating solution is poor and the service life is short. The main reasons are: ①The complexing ability of the complexing agent in the plating solution is not enough, and Ag ⁺ ions are easily reduced to simple silver under the conditions of light and heat; ②The properties of the complexing agent itself. Many complexing agents will deteriorate under the conditions of the electroplating process, such as the hydrolysis of succinimide under alkaline conditions. (4) The cost of the plating solution is high, and the industrial practical value is not high. The compounding agents and additives used in cyanide-free silver plating are expensive and difficult to purchase. Although the small tank experimental plating solution and coating performance are close to cyanide silver plating, it is difficult for manufacturers to accept it if it is used in actual production.

In the silver electroplating process, the base materials of silver-plated parts are generally copper and copper alloys, and steel is also used as the base for silver plating, but usually a layer of copper is first plated as the bottom coating. When active metal substrates such as copper and its alloys enter the silver plating solution, including cyanide silver plating solution and cyanide-free silver plating solution, the replacement silver layer formed on the surface of the plated parts not only seriously affects the bonding force between the coating and the substrate, but also The iron and copper ions generated during the replacement process can also contaminate the bath. Therefore, before the plated parts enter the silver plating solution in the traditional silver plating process, a pre-silvering layer must be carried out. Obviously, the traditional process not only further increases the cost of electroplating, but also takes time. One-step silver plating can simplify the silver plating process and save plating time, which may reduce operating costs and is beneficial to the practical application of cyanide-free silver plating systems in the electroplating industry.

Contents of the invention

The purpose of the present invention is to provide a kind of environment-friendly cyanide-free silver electroplating solution that does not contain cyanide. The proportioning composition and process conditions in the silver plating solution are:

Silver salt 0.01～1mol/L

Amino acid compounds or their derivatives 0.01～10mol/L

Auxiliary complexing agent 0.002～2mol/L.

Electroplating Additives 0.001～2.0g/L

pH of silver plating solution 6～14

The temperature of the silver plating solution is 10-70°C.

The described coordinating agent amino acid compounds or their derivatives preferably refer to glycine, α-alanine, β-alanine, cysteine, cystine, tyrosine, histidine, methionine, ortho One of aminobenzoic acid, aspartic acid, glutamic acid, sulfamic acid, nitrilodiacetic acid, nitrilotriacetic acid, diethyltriaminepentaacetic acid, N-hydroxyethylethylenediaminetriacetic acid, or aromatic ring amino acids One or more mixtures in any proportion.

The auxiliary agent refers to a mixture of one or more of succinimide, hydantoin, 5,5-dimethylhydantoin, uracil, cytosine or hypoxanthine in any proportion .

The electroplating additive refers to a mixture of one or more of soluble metal compounds, non-ionic surfactants, polyamine compounds, sulfur-containing compounds or nitrogen heterocyclic compounds in any proportion. Wherein the soluble metal compound refers to the mixture of one or more of the inorganic acid salt oxides or hydroxides of Bi, Co, Cd, Cu, Se or Sb in any proportion; the nonionic surfactant refers to polyethylene glycol (molecular weight 100-100000) or epoxy amine polycondensate (molecular weight 100-100000) or a mixture of two in any proportion; polyamine compounds refer to polyethyleneimine (molecular weight 100-100000) or Polyvinylamine (molecular weight: 100-100,000) or a mixture of two in any proportion; nitrogen heterocyclic compounds refer to isonicotinic acid, imidazole, benzimidazole, benzotriazole, 2-hydroxypyridine, 2 , a mixture of one or more of 2-bipyridine, uracil, uric acid, adenine or guanine in any proportion; sulfur-containing compounds refer to Na ₂ S ₂ O ₃ , K ₂ S ₂ O ₃ , thiourea, A mixture of one or more of ethylthiourea, aminothiazole, benzothiazole, mercaptobenzothiazole, mercaptobenzimidazole, thiodiethylene glycol or thiosalicylic acid in any proportion.

The present invention compares the remarkable advantage that background technology produces:

(1) Amino acid compounds and their derivatives are used as coordination agents to form coordination compounds with silver ions, which completely replace cyanide, eliminate the harm of cyanide to the human body and the environment during the electroplating process, and realize clean electroplating;

(2) The replacement rate of silver ions in the plating solution with active metal substrates such as copper and copper alloys is very slow, and the plated parts do not need to be pre-plated or immersed in silver, and a one-step silver plating process can be implemented, which simplifies the silver plating process and reduces generated cost;

(3) The raw material cost of the cyanide-free silver electroplating solution is low, the sources are wide, the plating layer is bonded reliably, and the plating solution has high stability performance, which can well meet the needs of the electroplating industry.

Detailed ways

Example 1

According to the composition of 0.15mol/L AgNO ₃ , 0.6mol/L β-alanine, 0.1mol/L uracil and 0.002g/L polyethyleneimine, dissolve each substance in deionized water to prepare an environment-friendly silver plating solution , adjust the pH of the silver plating solution to be 13, and the temperature of the silver plating solution to be 15°C. Immerse the copper or brass plated parts in the silver electroplating solution, and use the one-step electroplating method to electroplate the copper plated parts with a current density of 0.2A/ ^dm2 until the thickness of the silver layer is 3μm. The obtained silver layer is bright and has good bonding force with the matrix.

Example 2

Dissolve each substance in _deionized In the water, an environment-friendly silver electroplating solution is prepared, the pH of the silver plating solution is adjusted to be 10, and the temperature of the silver electroplating solution is 40°C. Immerse the copper or brass plated parts in the silver electroplating solution, and use the one-step electroplating method to electroplate the copper plated parts with a current density of 0.2A/ ^dm2 until the thickness of the silver layer is 3μm. The obtained silver layer is bright and has good bonding force with the matrix.

Example 3

Composition of 0.1mol/L AgSO ₃ CH ₃ , 0.5mol/L aminodiacetic acid, 0.1mol/L 5,5-dimethylhydantoin, 0.95g/L polyethyleneimine and 0.05g/L 10ppm Sb Each substance was dissolved in deionized water to prepare an environment-friendly silver electroplating solution, the pH of the silver plating solution was adjusted to be 8, and the temperature of the silver electroplating solution was 40°C. Immerse the brass plated parts in the silver electroplating solution, and use the one-step electroplating method to electroplate the copper plated parts with a current density of 0.2A/dm ² until the thickness of the silver layer is 3 μm. The obtained silver layer is bright and has good bonding force with the matrix.

Example 4

Dissolve each substance in deionized water according to the composition of 0.1mol/L AgNO ₃ , 0.5mol/L glutamic acid, 0.1mol/L uric acid, 0.01g/L polyethylene glycol and 2.0g/L 2,2-bipyridine, and prepare Become an environment-friendly silver electroplating solution, adjust the pH of the silver plating solution to be 6, and the temperature of the silver electroplating solution to be 65°C. Immerse the copper or brass plated parts in the silver electroplating solution, and use the one-step electroplating method to electroplate the copper plated parts with a current density of 0.2A/ ^dm2 until the thickness of the silver layer is 3μm. The obtained silver layer is bright and has good bonding force with the matrix.

Claims (9)

1, a kind of environmental non-cyanide plating solution for silver-plating, the composition proportioning and the processing condition that it is characterized in that not having in the cyanogen silver plating solution are:

Silver salt 0.01～1mol/L

Amino acids or derivatives thereof 0.01～10mol/L

Auxiliary complexing agent 0.002～2mol/L

Electroplating additive 0.001～2.0g/L

Silver plating liquid pH 6～14

10～70 ℃ of silver plating liquid temperature.

2, environmental non-cyanide plating solution for silver-plating according to claim 1 is characterized in that described coordination agent amino acids or derivatives thereof is excellent to be meant in glycine, α-Bing Ansuan, Beta-alanine, halfcystine, Gelucystine, network propylhomoserin, Histidine, methionine(Met), anthranilic acid, aspartic acid, L-glutamic acid, thionamic acid, ammonia oxalic acid, nitrilotriacetic acid(NTA), diethyl pentetic acid, N-hydroxyethyl-ethylenediamine nitrilotriacetic or the aromatic nucleus amino acid one or more.

3, environmental non-cyanide plating solution for silver-plating according to claim 1, it is characterized in that described auxiliary is meant succimide, glycolylurea, 5, the mixture of one or more arbitrary proportions in 5-T10, uridylic, cytosine(Cyt) or the xanthoglobulin.

4, environmental non-cyanide plating solution for silver-plating according to claim 1 is characterized in that described electroplating additive is meant the mixture of one or more arbitrary proportions in soluble metal compound, nonionogenic tenside, polyamine compound, sulfocompound or the nitrogen heterocyclic.

5, environmental non-cyanide plating solution for silver-plating according to claim 3 is characterized in that described soluble metal compound is meant the inorganic acid salt oxide compound of Bi, Co, Cd, Cu, Se or Sb or the mixture of one or more arbitrary proportions in the oxyhydroxide.

6, environmental non-cyanide plating solution for silver-plating according to claim 3 is characterized in that nonionogenic tenside is meant that molecular weight is that 100～100000 polyoxyethylene glycol or molecular weight are the mixture of one or both arbitrary proportions in 100～100000 the epoxy amine polycondensate.

7, environmental non-cyanide plating solution for silver-plating according to claim 3 is characterized in that polyamine compound is meant that molecular weight is that 100～100000 polymines or molecular weight are the mixture of one or both arbitrary proportions in 100～100000 the polyvinylamine.

8, environmental non-cyanide plating solution for silver-plating according to claim 3, it is characterized in that nitrogen heterocyclic is meant Yi Yansuan, imidazoles, benzoglyoxaline, benzotriazole, 2 hydroxy pyrimidine, 2, the mixture of one or more arbitrary proportions in 2-dipyridyl, uridylic, uric acid, VITAMIN B4 or the guanine.

9, environmental non-cyanide plating solution for silver-plating according to claim 3 is characterized in that sulfocompound is meant Na ₂S ₂O ₃, K ₂S ₂O ₃, one or more arbitrary proportions in thiocarbamide, ethyl thiourea, aminothiazole, benzothiazole, mercaptobenzothiazole, mercaptobenzimidazole, thio-diethylene glycol or the thiosalicylic acid mixture.