Cyanide-free cadmium plating bath solution, preparation method thereof and application of cyanide-free cadmium plating bath solution in cadmium plating

Abstract

The invention discloses a cyanide-free cadmium plating bath solution, a preparation method of the cyanide-free cadmium plating bath solution and application of the cyanide-free cadmium plating bath solution in cadmium plating. The cyanide-free cadmium plating bath solution comprises the following components according to the concentration: 50-70 g / L of cadmium chloride, 180-250 mL / L of an etidronic acid aqueous solution, 16-33 g / L of potassium sodium tartrate, 0.01-0.2 g / L of polyethylene glycol, 0.01-0.2 g / L of a brightener and 0.01-0.1 g / L of an additive HY. The method has the advantages that the bath solution is environment-friendly and non-toxic, wastewater treatment is simple, a plating layer is high in deposition speed, fine in crystallization and good in binding force, the problems that cyanide cadmium plating pollutes the environment, EDTA cadmium plating is poor in stability and the like are effectively solved, and the method has good application value and economic and social benefits.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment protection engineering, and in particular to a cyanide-free cadmium plating bath liquid used for electroplating a cadmium coating on a metal material, and also relates to a preparation method of the cyanide-free cadmium plating bath liquid and application of the cyanide-free cadmium plating bath liquid in cadmium plating. Background Art

[0002] Cadmium plating is the most economical and effective method to protect steel from corrosion under marine and hot and humid atmospheric conditions. The traditional cyanide cadmium plating solution is stable and has excellent coating performance, but it is gradually restricted because of its great harm to human body and environment. It is necessary to develop a cyanide-free cadmium plating system. In recent years, cadmium plating systems using aminocarboxylic acid ligands, 5,5-dimethylhydantoin (DMH), hydroxyethylidene diphosphonic acid (HEDP) and other ligands have gradually been used. Among them, HEDP is used as a ligand for Cd 2+ The ligand can be used alone to obtain a finely crystalline coating with bright and less brittle coating, excellent plating solution dispersion ability and depth ability, and is expected to replace cyanide cadmium plating.

[0003] At present, the more common ones are cyanide, aminocarboxylic acid compounds, organic acid compounds, etc. Triethanolamine cadmium plating has the problem of poor stability of the plating solution. Organic acid compounds such as HEDP are widely used in the electroplating industry and can form stable ligands with most metal ions. The coordination ability is second only to cyanide ions. The HEDP cyanide-free cadmium plating system has a simple plating solution composition, fast deposition rate, stable plating solution, bright coating, fine crystallization, good bonding with the steel surface, and can be directly plated on steel parts without pre-nickel plating. It has begun to develop rapidly in China.

[0004] Based on this, a new type of complexing agent is selected to replace cyanide cadmium plating, which can not only meet the environmental protection, but also avoid the interference of more impurity anions. At present, there is no report on the cadmium plating process using hydroxyethylidene diphosphonic acid as the main complexing agent and potassium sodium tartrate as the auxiliary. The present invention can obtain a coating with fine crystallization, good corrosion resistance and good flexibility. Summary of the invention

[0005] In view of the above-mentioned prior art, the purpose of the present invention is to overcome the deficiencies in the prior art and adapt to practical needs, thereby providing a cyanide-free cadmium plating bath, a preparation method thereof and an application thereof in cadmium plating.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A cyanide-free cadmium plating bath comprising the following components in terms of concentration: 50~70 g / L cadmium chloride, 180~250 mL / L hydroxyethylidene diphosphonic acid aqueous solution, 16~33 g / L potassium sodium tartrate, 0.01~0.2 g / L polyethylene glycol, 0.01~0.2 g / L brightener and 0.01~0.1g / L additive HY.

[0007] Furthermore, the cadmium chloride is 50 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 180 mL / L, potassium sodium tartrate is 16 g / L, polyethylene glycol is 0.01 g / L, the brightener is 0.01 g / L, and the additive HY is 0.01 g / L.

[0008] Furthermore, the cadmium chloride is 70 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 250 mL / L, the potassium sodium tartrate is 33 g / L, the polyethylene glycol is 0.2 g / L, the brightener is 0.2 g / L, and the additive HY is 0.1 g / L.

[0009] Furthermore, the cadmium oxide is 60 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 220 mL / L, the potassium sodium tartrate is 28 g / L, the polyethylene glycol is 0.1 g / L, the brightener is 0.1 g / L, and the additive HY is 0.05 g / L.

[0010] Furthermore, the cadmium oxide is 50 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 250 mL / L, potassium sodium tartrate is 30 g / L, polyethylene glycol is 0.01 g / L, the brightener is 0.2 g / L, and the additive HY is 0.1 g / L.

[0011] Furthermore, the mass fraction of the hydroxyethylidene diphosphonic acid aqueous solution is 60%.

[0012] A method for preparing a cyanide-free cadmium plating bath comprises the following steps: (1) According to the required volume of the tank solution, add 5% deionized water to the aqueduct, then add 180-250 mL / L of the 60% mass fraction hydroxyethylidene diphosphonic acid aqueous solution as described above, and stir evenly; (2) Take 16-33 g / L of potassium sodium tartrate as described above, take another water tank, use 5% of the volume of deionized water required to prepare the tank solution, and dissolve the potassium sodium tartrate completely at room temperature; (3) Take 50-70 g / L of the cadmium chloride described above, take another water tank, use 10% of the volume of deionized water required to prepare the tank solution, and dissolve the cadmium chloride alone at room temperature; (4) sequentially adding the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) into the aqueduct after being stirred evenly in step (1), and stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (5) adjusting the pH value of the bath solution obtained in step (4) to 12-12.5 with a 50% by mass potassium hydroxide solution or a 10% by mass dilute sulfuric acid solution, and sequentially adding 0.01-0.2 g / L of the polyethylene glycol, 0.01-0.2 g / L of the brightener, and 0.01-0.1 g / L of the additive HY as described above, and stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) Deionized water is added to the bath solution obtained in step (5) until the desired volume of the plating solution is reached, thereby obtaining a cyanide-free cadmium plating bath solution.

[0013] Further, after the cyanide-free cadmium plating bath solution is prepared, the maintenance parameters of the power-on treatment are: current density 0.02~0.5A / dm 2 , processing time 24h.

[0014] Application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform conventional pretreatment of the workpiece: the workpiece is sequentially subjected to sandpaper grinding, water washing, chemical degreasing, hot water washing, cold water washing, pickling, water washing, activation, and water washing to obtain the pretreated workpiece; (2) The pre-treated workpiece obtained in step (1) is subjected to a current density of 0.6 to 1.5 A / dm 2 , placing it in the above-mentioned cyanide-free cadmium plating bath for conventional electroplating for 40 to 60 minutes at a temperature of 35 to 45°C, using a cadmium plate as the anode, and the area ratio of the cathode to the anode is 1:2; (3) The workpiece treated in step (2) is sequentially washed with cold water, washed with hot water and dried, thereby completing the application of the cyanide-free cadmium plating bath solution in the electroplated cadmium layer.

[0015] Furthermore, the chemical degreasing, hot water washing and cold water washing are specifically as follows: the workpiece to be plated with cadmium is placed in a chemical degreasing solution at 60 to 70° C. for 10 to 15 minutes, and then thoroughly washed with warm water, and then washed with cold water after warm water to obtain a degreasing sample; The specific steps of pickling and water washing are as follows: the degreased sample is immediately placed in a hydrochloric acid pickling solution with a volume concentration of 15% and immersed for 1 to 2 minutes, and then rinsed with cold water to obtain the pickled sample; The activation and water washing treatments are as follows: the acid-washed sample is immersed in a hydrochloric acid activation solution with a volume concentration of 10% for 30 to 60 seconds, and then thoroughly washed with deionized water to obtain an activated sample.

[0016] Furthermore, the chemical degreasing liquid is prepared from 55-80 g / L sodium hydroxide, 35-55 g / L trisodium phosphate, 30-50 g / L sodium carbonate, 10-30 g / L sodium silicate and deionized water.

[0017] The beneficial effects of the present invention are as follows: compared with the prior art, the present invention has obvious advantages and beneficial effects. It can be seen from the above technical scheme that the present invention uses cadmium chloride as the main salt, hydroxyethylidene diphosphonic acid as the coordination agent, and potassium sodium tartrate as the auxiliary coordination agent to electroplating cadmium in an alkaline environment. The bath solution is environmentally friendly and non-toxic, the wastewater treatment is simple, and the coating deposition speed is fast, the crystallization is fine, and the bonding strength is good. 1 A / dm 2 The plating speed under the current density reaches 18 μm / h. The invention effectively avoids many problems such as environmental pollution caused by cyanide cadmium plating and poor stability of EDTA cadmium plating, and has good application value and economic and social benefits. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0019] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium chloride 60 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 218 mL / L, potassium sodium tartrate 20 g / L, polyethylene glycol 0.05 g / L, brightener 0.1 g / L and additive HY 0.02 g / L.

[0020] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% deionized water to the aqueduct according to the volume of the plating solution, add 218 mL / L of a 60% hydroxyethylidene diphosphonic acid aqueous solution as described in the present embodiment and stir evenly; (2) Take another water tank and use 5% deionized water to prepare the required bath solution volume to dissolve 20 g / L potassium sodium tartrate as described in the present embodiment at room temperature until it is completely dissolved; (3) Take another water tank and use 10% deionized water to prepare the required bath solution volume to dissolve 60 g / L cadmium chloride as described in the present embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in steps (2) and (3) to the bath solution stirred evenly in step (1) in sequence, and stir at room temperature until the bath solution is dissolved and becomes clear and transparent; (5) Use a 10% dilute sulfuric acid solution or a 50% potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12, and after cooling to room temperature, add 0.05 g / L polyethylene glycol and 0.1 g / L brightener and 0.02 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) adding deionized water to the bath solution obtained in step (5) to the required volume of the plating solution to obtain a cyanide-free cadmium plating bath solution.

[0021] Preferably, after the cyanide-free cadmium plating bath is prepared, 0.02 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0022] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after sanding, and then place it in a 70°C chemical degreasing solution for 15 minutes, wherein the chemical degreasing solution is composed of 70 g / L sodium hydroxide, 40 g / L trisodium phosphate, 40 g / L sodium carbonate, and 10 g / L sodium silicate; after degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water after thorough washing with warm or hot water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immersed in the pickling solution (15 vol% HCl) for 1 minute, then washed with running water, and then immersed in the activation solution (10 vol% HCl) for 30 seconds; then it is thoroughly washed with deionized water; (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 40°C with a pressure of 1.2 A / dm 2 The current density was used for electroplating for 40 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0023] Through the above process, a fine, uniform, well-bonded gray-white coating can be obtained on the surface of the substrate. The main salt content in this system is low, and the coating deposition speed is slightly slow, with a plating speed of about 0.3 μm / min. Example

[0024] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium chloride 70 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 250 mL / L, potassium sodium tartrate 33 g / L, polyethylene glycol 0.2 g / L, brightener 0.2 g / L and additive HY 0.1 g / L.

[0025] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% of deionized water to the aqueduct according to the required volume of the tank solution, add 250 mL / L of the 60% hydroxyethylidene diphosphonic acid aqueous solution as described above in this embodiment, and stir evenly; (2) Take another water tank, use 5% of the required volume of deionized water to dissolve 33 g / L of potassium sodium tartrate as described above in this embodiment at room temperature until it is completely dissolved; (3) Take another water tank, use 10% of the required volume of deionized water to dissolve 70 g / L of cadmium chloride as described above in this embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) in turn to the tank solution stirred evenly in step (1), and stir at room temperature until the tank solution is dissolved and becomes clear and transparent; (5) Use 10% of the mass fraction of dilute sulfuric acid solution or 50% of the mass fraction of potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12.5, cool to room temperature, and add 0.2 g / L polyethylene glycol, 0.2 g / L brightener and 0.1 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) adding deionized water to the bath solution obtained in step (5) to the required volume of the plating solution to obtain a cyanide-free cadmium plating bath solution.

[0026] Preferably, after the cyanide-free cadmium plating bath is prepared, a 0.5 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0027] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after grinding, and then place it in a chemical degreasing solution at 70°C for 15 minutes. The chemical degreasing solution consists of 80 g / L sodium hydroxide, 55 g / L trisodium phosphate, 50 g / L sodium carbonate, and 30 g / L sodium silicate. After degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immersed in a pickling solution (15 vol% HCl) for 2 minutes, then washed with running water, and then immersed in an activation solution (10 vol% HCl) for 60 seconds. After that, it is thoroughly washed with deionized water. (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 40°C with a pressure of 1.5 A / dm 2 The current density was used for electroplating for 40 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0028] Through the above process, a gray-white coating with fine crystals and good softness can be obtained on the surface of the substrate. The coating deposition rate is about 0.46 μm / min, and the coating does not crack when bent 180°. Example

[0029] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium oxide 50 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 180 mL / L, potassium sodium tartrate 16 g / L, polyethylene glycol 0.01 g / L, brightener 0.01 g / L and additive HY 0.01 g / L.

[0030] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% deionized water to the aqueduct according to the volume of the plating solution, add 180 mL / L of the 60% hydroxyethylidene diphosphonic acid aqueous solution as described above in the present embodiment, and stir evenly; (2) Take another water tank, use 5% of the required volume of deionized water to dissolve the 16 g / L potassium sodium tartrate as described above in the present embodiment at room temperature until it is completely dissolved; (3) Take another water tank, use 10% of the required volume of deionized water to dissolve the 50 g / L cadmium chloride as described above in the present embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) to the bath solution stirred evenly in step (1) in sequence, and stir at room temperature until the bath solution is dissolved and becomes clear and transparent; (5) Use 10% of the mass fraction of dilute sulfuric acid solution or 50% of the mass fraction of potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12.0-12.5, cool to room temperature, and add 0.01% of the mass fraction of potassium hydroxide as described above in the present embodiment; g / L polyethylene glycol, 0.01 g / L brightener and 0.01 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) adding deionized water to the bath solution obtained in step (5) to prepare the required volume of plating solution to obtain a cyanide-free cadmium plating bath solution.

[0031] Preferably, after the cyanide-free cadmium plating bath is prepared, 0.02-0.5 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0032] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after sanding, and then place it in a 60°C chemical degreasing solution for 10 minutes, wherein the chemical degreasing solution is composed of 55 g / L sodium hydroxide, 35 g / L trisodium phosphate, 30 g / L sodium carbonate, and 10 g / L sodium silicate; after degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water after thorough washing with warm or hot water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immersed in a pickling solution (15 vol% HCl) for 1 minute, then washed with running water, and then immersed in an activation solution (10 vol% HCl) for 45 seconds; then it is thoroughly washed with deionized water; (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 40°C with a pressure of 0.6 A / dm 2The current density was used for electroplating for 40 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0033] The above process can also obtain a bright white coating with fine crystals and good softness on the surface of the substrate, and the coating deposition rate is about 0.20 μm / min. Example

[0034] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium oxide 60 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 218 mL / L, potassium sodium tartrate 30 g / L, polyethylene glycol 0.05 g / L, brightener 0.05 g / L and additive HY 0.01 g / L.

[0035] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% deionized water to the aqueduct according to the volume of the plating solution, add 218 mL / L of the 60% hydroxyethylidene diphosphonic acid aqueous solution as described above in the present embodiment, and stir evenly; (2) Take another water tank, use 5% of the required volume of deionized water to dissolve 30 g / L of potassium sodium tartrate as described above in the present embodiment at room temperature until it is completely dissolved; (3) Take another water tank, use 10% of the required volume of deionized water to dissolve 60 g / L of cadmium chloride as described above in the present embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) in turn to the bath solution stirred evenly in step (1), and stir at room temperature until the bath solution is dissolved and becomes clear and transparent; (5) Use 10% of the mass fraction of dilute sulfuric acid solution or 50% of the mass fraction of potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12-12.5, cool to room temperature, and add 0.05% of the mass fraction of potassium hydroxide as described above in the present embodiment; g / L polyethylene glycol, 0.05 g / L brightener and 0.01 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent, (6) adding deionized water to the bath solution obtained in step (5) to the required volume of the plating solution to obtain a cyanide-free cadmium plating bath solution.

[0036] Preferably, after the cyanide-free cadmium plating bath is prepared, 0.3 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0037] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after sanding, and then place it in a 65°C chemical degreasing solution for 15 minutes, wherein the chemical degreasing solution is composed of 60 g / L sodium hydroxide, 35 g / L trisodium phosphate, 40 g / L sodium carbonate, and 10 g / L sodium silicate; after degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water after thorough washing with warm or hot water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immersed in the pickling solution (15 vol% HCl) for 1 minute and then washed with running water, and then immersed in the activation solution (10 vol% HCl) for 30 to 60 seconds; then it is thoroughly washed with deionized water; (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 35°C with a pressure of 0.6A / dm 2 The current density was used for electroplating for 60 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0038] Through the above process, a bright white coating with fine crystals, uniform brightness and good softness can be obtained on the surface of the substrate; at this time, the coating deposition rate reaches 0.25 μm / min, and the coating does not crack when bent 180°. Example

[0039] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium chloride 60 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 220 mL / L, potassium sodium tartrate 28 g / L, polyethylene glycol 0.1 g / L, brightener 0.1 g / L and additive HY 0.05 g / L.

[0040] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% of deionized water to the aqueduct according to the required volume of the tank solution, add 220 mL / L of the 60% hydroxyethylidene diphosphonic acid aqueous solution as described above in this embodiment, and stir evenly; (2) Take another water tank, use 5% of the required volume of deionized water to dissolve 28 g / L of potassium sodium tartrate as described above in this embodiment at room temperature until it is completely dissolved; (3) Take another water tank, use 10% of the required volume of deionized water to dissolve 60 g / L of cadmium chloride as described above in this embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) in turn to the tank solution stirred evenly in step (1), and stir at room temperature until the tank solution is dissolved and becomes clear and transparent; (5) Use 10% of the mass fraction of dilute sulfuric acid solution or 50% of the mass fraction of potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12.2, cool to room temperature, and add 0.1% of the mass fraction of potassium hydroxide as described above in this embodiment; g / L polyethylene glycol, 0.1 g / L brightener and 0.05 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) adding deionized water to the bath solution obtained in step (5) to the required volume of the plating solution to obtain a cyanide-free cadmium plating bath solution.

[0041] Preferably, after the cyanide-free cadmium plating bath is prepared, a 0.5 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0042] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after sanding, and then place it in a 68°C chemical degreasing solution for 12 minutes, wherein the chemical degreasing solution is composed of 70 g / L sodium hydroxide, 40 g / L trisodium phosphate, 40 g / L sodium carbonate, and 10 g / L sodium silicate; after degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water after thorough washing with warm or hot water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immersed in the pickling solution (15 vol% HCl) for 1 minute, then washed with running water, and then immersed in the activation solution (10 vol% HCl) for 40 seconds; then it is thoroughly washed with deionized water; (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 45°C with 1A / dm 2 The current density was used for electroplating for 40 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0043] Through the above process, a gray-white coating with fine crystals and good softness can be obtained on the surface of the substrate. The coating deposition rate is about 0.30 μm / min, and the coating does not crack when bent 180°. Example

[0044] The present invention provides a cyanide-free cadmium plating bath solution, which comprises the following raw materials in terms of concentration: Cadmium chloride 50 g / L, 60% hydroxyethylidene diphosphonic acid aqueous solution 250 mL / L, potassium sodium tartrate 30 g / L, polyethylene glycol 0.01 g / L, brightener 0.2 g / L and additive HY 0.1 g / L.

[0045] In this embodiment, the present invention also provides a method for preparing a cyanide-free cadmium plating bath solution, comprising the following steps: (1) After adding 5% of deionized water to the aqueduct according to the required volume of the tank solution, add 250 mL / L of the 60% hydroxyethylidene diphosphonic acid aqueous solution as described above in this embodiment, and stir evenly; (2) Take another water tank, use 5% of the required volume of deionized water to dissolve 30 g / L of potassium sodium tartrate as described above in this embodiment at room temperature until it is completely dissolved; (3) Take another water tank, use 10% of the required volume of deionized water to dissolve 50 g / L of cadmium chloride as described above in this embodiment at room temperature until it is completely dissolved; (4) Add the potassium sodium tartrate and cadmium chloride dissolved in steps (2) and (3) to the tank solution stirred evenly in step (1) in sequence, and stir at room temperature until the tank solution is dissolved and becomes clear and transparent; (5) Use 10% of the mass fraction of dilute sulfuric acid solution or 50% of the mass fraction of potassium hydroxide solution to adjust the pH value of the solution obtained in step (4) to 12.5, cool to room temperature, and add 0.01% of the mass fraction of potassium hydroxide as described above in this embodiment; g / L polyethylene glycol, 0.2 g / L brightener and 0.1 g / L additive HY, stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) adding deionized water to the bath solution obtained in step (5) to the required volume of the plating solution to obtain a cyanide-free cadmium plating bath solution.

[0046] Preferably, after the cyanide-free cadmium plating bath is prepared, 0.02 A / dm 2 Cadmium plating is carried out after a small current treatment for 24 hours.

[0047] In this embodiment, the present invention further provides an application of a cyanide-free cadmium plating bath in cadmium plating, the application comprising the following steps: (1) Perform routine pretreatment of the workpiece: sandpaper the Q235 steel plate sample to be plated with cadmium, wash it with water after sanding, and then place it in a 70°C chemical degreasing solution for 11 minutes, wherein the chemical degreasing solution is composed of 70 g / L sodium hydroxide, 40 g / L trisodium phosphate, 40 g / L sodium carbonate, and 10 g / L sodium silicate; after degreasing, the parts are thoroughly washed with warm or hot water, and then washed with cold water after thorough washing with warm or hot water. The cold water washing process must ensure that the entire surface of the parts is hydrophilic. If the water film is continuous for more than 60 seconds, the degreasing is considered qualified. The degreasing sample is immediately immersed in the pickling solution (15 vol% HCl) for 1.5 minutes, then washed with running water, and then immersed in the activation solution (10 vol% HCl) for 45 seconds; then thoroughly washed with deionized water; (2) The sample treated in step (1) is placed in the cyanide-free cadmium plating bath described above in this embodiment at 42°C with 1A / dm 2 The current density was used for electroplating for 40 min, a cadmium plate was used as the anode, and the area ratio of the cathode to the anode was 1:2; (3) The sample plated in step (2) is washed thoroughly with deionized water (i.e., washed with cold water), washed with hot water, and dried with cold air (i.e., dried), thereby completing the application of the cyanide-free cadmium plating bath in cadmium plating.

[0048] The above process can obtain a gray-white coating with fine crystals and good softness on the surface of the substrate. The coating deposition rate is about 0.21 μm / min, and the coating does not crack when bent 180°.

[0049] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of the technical solution of the present invention. The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A cyanide-free cadmium plating bath, characterized in that: Contains the following components in concentration: 50~70 g / L cadmium chloride, 180~250 mL / L hydroxyethylidene diphosphonic acid aqueous solution, 16~33 g / L potassium sodium tartrate, 0.01~0.2 g / L polyethylene glycol, 0.01~0.2 g / L brightener and 0.01~0.1g / L additive HY.

2. The cyanide-free cadmium plating bath according to claim 1, wherein: The cadmium chloride is 50 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 180 mL / L, potassium sodium tartrate is 16 g / L, polyethylene glycol is 0.01 g / L, the brightener is 0.01 g / L, and the additive HY is 0.01 g / L.

3. The cyanide-free cadmium plating bath according to claim 1, wherein: The cadmium chloride is 70 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 250 mL / L, potassium sodium tartrate is 33 g / L, polyethylene glycol is 0.2 g / L, brightener is 0.2 g / L, and additive HY is 0.1 g / L.

4. The cyanide-free cadmium plating bath according to claim 1, wherein: The cadmium oxide is 60 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 220 mL / L, potassium sodium tartrate is 28 g / L, polyethylene glycol is 0.1 g / L, the brightener is 0.1 g / L, and the additive HY is 0.05 g / L.

5. The cyanide-free cadmium plating bath according to claim 1, wherein: The cadmium oxide is 50 g / L, the hydroxyethylidene diphosphonic acid aqueous solution is 250 mL / L, potassium sodium tartrate is 30 g / L, polyethylene glycol is 0.01 g / L, the brightener is 0.2 g / L, and the additive HY is 0.1 g / L.

6. The cyanide-free cadmium plating bath according to any one of claims 1 to 5, characterized in that: The mass fraction of the hydroxyethylidene diphosphonic acid aqueous solution is 60%.

7. A method for preparing a cyanide-free cadmium plating bath, characterized in that: The following steps are involved: (1) After adding 5% deionized water to the aqueduct according to the required volume of the tank solution, add 180-250 mL / L of a 60% by mass aqueous solution of hydroxyethylidene diphosphonic acid as described in any one of claims 1 to 6, and stir evenly; (2) Take 16-33 g / L of potassium sodium tartrate as described in any one of claims 1 to 6, take another water tank, use 5% of the volume of deionized water required to prepare the tank solution, and dissolve the potassium sodium tartrate completely at room temperature; (3) Take 50-70 g / L of the cadmium chloride as described in any one of claims 1 to 6, take another water tank, use deionized water that accounts for 10% of the required volume of the tank solution, and dissolve the cadmium chloride alone at room temperature; (4) sequentially adding the potassium sodium tartrate and cadmium chloride dissolved in step (2) and step (3) into the aqueduct after being stirred evenly in step (1), and stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (5) adjusting the pH value of the bath solution obtained in step (4) to 12-12.5 with a 50% by mass potassium hydroxide solution or a 10% by mass dilute sulfuric acid solution, and adding 0.01-0.2 g / L of polyethylene glycol as described in any one of claims 1 to 6, 0.01-0.2 g / L of a brightener, and 0.01-0.1 g / L of an additive HY in sequence after cooling to room temperature, and stirring at room temperature until the bath solution is dissolved and becomes clear and transparent; (6) Deionized water is added to the bath solution obtained in step (5) until the desired volume of the plating solution is reached, thereby obtaining a cyanide-free cadmium plating bath solution.

8. The method for preparing the cyanide-free cadmium plating bath according to claim 7, wherein: After the cyanide-free cadmium plating bath solution is prepared, the power-on treatment maintenance parameters are: current density 0.02~0.5 A / dm 2 , processing time 24h.

9. Application of a cyanide-free cadmium plating bath in cadmium plating, characterized in that: The application includes the following steps: (1) Perform conventional pretreatment of the workpiece: the workpiece is sequentially subjected to sandpaper grinding, water washing, chemical degreasing, hot water washing, cold water washing, pickling, water washing, activation, and water washing to obtain the pretreated workpiece; (2) The pre-treated workpiece obtained in step (1) is subjected to a current density of 0.6 to 1.5 A / dm 2 , placing it in the cyanide-free cadmium plating bath as described in any one of claims 1 to 8 for conventional electroplating for 40 to 60 minutes at a temperature of 35 to 45° C., using a cadmium plate as the electroplating anode, and the area ratio of the cathode to the anode is 1:2; (3) The workpiece treated in step (2) is sequentially washed with cold water, washed with hot water and dried, thereby completing the application of the cyanide-free cadmium plating bath solution in the electroplated cadmium layer.

10. Use of the cyanide-free cadmium plating bath according to claim 9 in cadmium plating, characterized in that: The chemical degreasing, hot water washing and cold water washing are specifically as follows: the workpiece to be plated with cadmium is placed in a chemical degreasing solution at 60 to 70° C. for 10 to 15 minutes, and then thoroughly washed with warm water, and then washed with cold water to obtain a degreasing sample; The specific steps of pickling and water washing are as follows: the degreased sample is immediately placed in a hydrochloric acid pickling solution with a volume concentration of 15% and immersed for 1 to 2 minutes, and then rinsed with cold water to obtain the pickled sample; The activation and water washing treatments are as follows: the acid-washed sample is immersed in a hydrochloric acid activation solution with a volume concentration of 10% for 30 to 60 seconds, and then thoroughly washed with deionized water to obtain an activated sample.

11. Use of the cyanide-free cadmium plating bath according to claim 10 in cadmium plating, characterized in that: The chemical degreasing liquid is prepared from 55-80 g / L sodium hydroxide, 35-55 g / L trisodium phosphate, 30-50 g / L sodium carbonate, 10-30 g / L sodium silicate and deionized water.