An electroplating bath for CdZr alloy coating on a metal surface and a preparation method thereof

Abstract

The present invention provides an electroplating bath for a CdZr alloy coating on a metal surface, which comprises the following components: cadmium ions 50 - 80 g / L; zirconium ions 5 - 10 g / L; sodium aminosulfonate 10 - 20 g / L; cyclohexanediaminetetraacetic acid 15 - 30 g / L; 2-mercaptobenzimidazole 0.01 - 0.05 g / L; reinforcing nanoparticles 0.1 - 0.7 g / L; cetyltrimethylammonium bromide 0.01 - 0.05 g / L; ionic complex macromolecular surfactant 0.01 - 0.05 g / L; pH regulator 5 - 25 g / L; the balance being water; and the pH of the electroplating bath is 4 - 6. Adding reinforcing nanoparticles to the electroplating bath can improve the hardness and friction properties of the coating; the combination of cetyltrimethylammonium bromide and ionic complex macromolecular surfactant is conducive to the uniform dispersion of the nanoparticles in the bath, thereby improving the coating uniformity.

Description

Technical Field

[0001] The present invention belongs to the field of coating protection, and particularly relates to an electroplating bath for a CdZr alloy coating on a metal surface and a preparation method thereof. Background Art

[0002] The cadmium coating is a sacrificial anode protection coating with excellent corrosion resistance in marine environments and is widely used for the protection of steel structures of ships and vessels. Chinese Patent CN110205629A discloses a heavy anti-corrosion cadmium-cobalt alloy and graphene sealing coating, which is characterized in that: it includes a metal substrate, a cadmium-cobalt alloy coating prepared on the metal substrate, a passivation layer formed on the cadmium-cobalt alloy coating, and a graphene sealing layer formed on the passivation layer. The cadmium-cobalt alloy electroplating process is as follows: cadmium chloride 20 - 40 g / L, cobalt chloride 2 - 15 g / L, complexing agent 90 - 160 g / L, potassium chloride 120 - 180 g / L, brightening agent 1 - 3 mL / L, auxiliary agent 20 - 40 mL / L, leveling agent 5 - 15 mL / L; the pH value of the plating bath is 6.5 - 7.5, the plating bath temperature is 20°C - 35°C, the cathode current density is 0.5 - 2 A / dm 2 , the ratio of the cathode area to the anode area is 2:(1 - 3), and the anode uses a cadmium anode plate with a cadmium content ≥ 99.97%. "The influence of cyanide-free electroplating of cadmium-titanium alloy on the hydrogen embrittlement performance of steel substrate" studied the influence of the cyanide-free electroplating cadmium-titanium alloy process on the hydrogen embrittlement performance of A100 steel substrate. The electroplating cadmium-titanium alloy solution formula and operating conditions are: metallic titanium (added in the form of Ti 4+ form) 2 - 5 g / L, metallic cadmium (added in the form of cadmium chloride) 15 - 25 g / L, ethylenediaminetetraacetic acid 30 - 40 g / L, nitrilotriacetic acid 100 - 130 g / L, ammonium chloride 100 - 130 g / L, ammonium acetate 20 - 30 g / L, J κ 2 - 3 A / dm 2 , θ 15 - 35°C, U 2 - 5 V. The common cadmium alloy coatings in the prior art are basically for cadmium-cobalt alloy coatings, cadmium-titanium alloy coatings, and cadmium-nickel alloy coatings. How to improve the cadmium coating remains a research focus in the prior art. After searching by the applicant, the prior art does not involve how to electroplate a cadmium-zirconium alloy coating. Although electroplating cadmium is relatively mature, there is not much to learn from regarding how to improve it. Summary of the Invention

[0003] In order to solve the deficiencies existing in the prior art, the purpose of the present invention is to provide an electroplating bath for a CdZr alloy coating on a metal surface and a preparation method thereof, and a CdZr alloy coating with excellent properties is prepared, which can meet the uses of anti-corrosion and coating protection.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] An electroplating solution for a CdZr alloy coating on a metal surface, comprising the following components:

[0006] Cadmium ions: 50 - 80 g / L;

[0007] Zirconium ions: 5 - 10 g / L;

[0008] Sodium sulfamate: 10 - 20 g / L;

[0009] Cyclohexanediaminetetraacetic acid: 15 - 30 g / L;

[0010] 2-Mercaptobenzimidazole: 0.01 - 0.05 g / L;

[0011] Reinforcing nanoparticles: 0.1 - 0.7 g / L;

[0012] Cetyltrimethylammonium bromide: 0.01 - 0.05 g / L;

[0013] Ionic complex macromolecular surfactant: 0.01 - 0.05 g / L;

[0014] pH regulator: 5 - 25 g / L;

[0015] The balance is water;

[0016] The pH of the electroplating solution is 4 - 6.

[0017] Furthermore, the metal substrate is steel, aluminum or magnesium.

[0018] Furthermore, the cadmium ions are selected from one or more of cadmium sulfate and cadmium chloride.

[0019] Furthermore, the zirconium ions are selected from one or more of zirconium sulfate and zirconium chloride.

[0020] Furthermore, the reinforcing nanoparticles are selected from one or more of WC and TiC; more preferably, the particle size of the reinforcing nanoparticles is 100 - 500 nm.

[0021] Furthermore, the pH regulator is selected from one or more of hydrochloric acid and sulfuric acid.

[0022] More preferably, an electroplating solution for a CdZr alloy coating on a metal surface, comprising the following components:

[0023] Cadmium ions: 60 - 70 g / L;

[0024] Zirconium ions: 7 - 8 g / L;

[0025] Sodium sulfamate: 13 - 17 g / L;

[0026] Cyclohexanediaminetetraacetic acid: 20 - 25 g / L;

[0027] 2-mercaptobenzimidazole 0.02 - 0.03 g / L;

[0028] Reinforcing nanoparticles 0.3 - 0.5 g / L;

[0029] Cetyltrimethylammonium bromide 0.02 - 0.03 g / L;

[0030] Ionic complex macromolecular surfactant 0.02 - 0.03 g / L;

[0031] pH regulator 10 - 20 g / L;

[0032] The balance is water;

[0033] The pH of the electroplating solution is 4.5 - 5.5.

[0034] A method for preparing a CdZr alloy coating on a metal surface, comprising the following steps:

[0035] (1) Pretreatment of the metal substrate;

[0036] (2) Preparation of the electroplating solution: Place a part of water in a container, heat it to 30 - 40 °C, and while stirring, add cetyltrimethylammonium bromide and ionic complex macromolecular surfactant respectively. Subsequently, add the reinforcing particles and continuously stir for 1 - 3 min to make them disperse evenly; sequentially add cadmium ions, zirconium ions, sodium aminosulfonate, cyclohexanediaminetetraacetic acid, and 2-mercaptobenzimidazole to the remaining water. After stirring evenly, add the previously prepared dispersion liquid, and add a pH regulator during continuous stirring to adjust the pH value of the electroplating solution, thus obtaining the electroplating solution;

[0037] (3) Place the metal substrate in the electroplating bath for electroplating.

[0038] (4) After electroplating, wash and dry the metal substrate.

[0039] Further, the step (1) includes grinding the metal substrate, removing rust with an acidic solution, sandblasting, degreasing, and ultrasonic cleaning with deionized water, and heating it to 40 - 50 °C after drying.

[0040] Further, in the step (3), the metal substrate is used as the cathode, the graphite plate is used as the anode, the distance between the cathode and the anode is 10 - 15 cm, the current density is 5 - 10 A / cm 2 , the temperature of the electroplating solution is 40 - 50 °C, and the electroplating time is 10 - 30 min.

[0041] A CdZr alloy coating on a metal surface, prepared by the above preparation method, wherein the Cd content in the CdZr alloy coating is 70-80 wt.%, the Zr content is 20-30 wt.%, the content of reinforcing particles is 0.7-1.5 wt.%, and the thickness of the CdZr alloy coating is 5-18 μm.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) By optimizing and adjusting the composition and content of the electroplating bath, the present invention prepares a CdZr alloy coating with excellent performance, which can be widely used for the protection of metal components.

[0044] (2) By adding reinforcing nanoparticles to the electroplating bath, the present invention can improve the hardness and friction properties of the coating; since the nanoparticles are prone to agglomeration in the bath, the present invention uses cetyltrimethylammonium bromide and an ionic complex macromolecular surfactant for compounding, which is beneficial to the uniform dispersion of the nanoparticles in the bath, thereby improving the coating uniformity.

[0045] (3) The present invention uses cyclohexanediaminetetraacetic acid as a complexing agent, and experiments show that this complexing agent can achieve good technical effects. Specific Embodiments

[0046] The present invention will be described in detail below with reference to specific embodiments. Here, the illustrative embodiments of the present invention and the descriptions are used to explain the present invention, but do not limit the present invention.

[0047] Example 1

[0048] A preparation method of a CdZr alloy coating on a metal surface, characterized by comprising the following steps:

[0049] (1) Pretreatment of the metal substrate: The metal substrate is polished, pickled with an acidic solution, sandblasted, degreased, and ultrasonically cleaned with deionized water, and then heated to 40 °C after drying.

[0050] (2) Preparation of the electroplating bath: Place a part of water in a container, heat it to 30 °C, and add 0.01 g of cetyltrimethylammonium bromide and 0.01 g of an ionic complex macromolecular surfactant respectively during stirring. Then add 0.1 g of WC particles with a particle size of 100 nm, and continuously stir for 1 min to make it uniformly dispersed; sequentially add cadmium sulfate calculated according to 50 g of cadmium ions, zirconium sulfate calculated according to 50 g of zirconium ions, 10 g of sodium aminosulfonate, 15 g of cyclohexanediaminetetraacetic acid, and 0.01 g of 2-mercaptobenzimidazole to the remaining water (1 L in total), stir evenly, and then add the previously prepared dispersion liquid. During continuous stirring, add a pH regulator to adjust the pH value of the electroplating bath with dilute sulfuric acid to 4, and the electroplating bath is obtained;

[0051] (3) Place the metal substrate in the electroplating bath for electroplating; use the metal substrate as the cathode, a graphite plate as the anode, the distance between the cathode and the anode is 10 cm, and the current density is 5 A / cm 2 , the temperature of the electroplating bath is 40 °C, and the electroplating time is 10 min.

[0052] (4) After electroplating, wash and dry the metal substrate.

[0053] Example 2

[0054] A method for preparing a CdZr alloy coating on a metal surface, characterized by comprising the following steps:

[0055] (1) Pretreatment of the metal substrate: Grind the metal substrate, remove rust with an acidic solution, sandblast, degrease, and ultrasonically clean with deionized water, and heat to 50 °C after drying.

[0056] (2) Prepare the electroplating bath: Place a portion of water in a container, heat to 40 °C, and add 0.05 g of cetyltrimethylammonium bromide and 0.05 g of an ionic complex macromolecular surfactant respectively during stirring. Subsequently, add 0.7 g of WC particles with a particle size of 500 nm, and continuously stir for 3 min to make it evenly dispersed; sequentially add cadmium sulfate calculated according to 80 g of cadmium ions, zirconium sulfate calculated according to 80 g of zirconium ions, 10 g of sodium aminosulfonate, 30 g of cyclohexanediaminetetraacetic acid, and 0.05 g of 2-mercaptobenzimidazole to the remaining water (a total of 1 L), stir evenly, then add the previously prepared dispersion liquid, and add a pH regulator during continuous stirring to adjust the pH value of the electroplating bath to 6 with dilute sulfuric acid, thus obtaining the electroplating bath;

[0057] (3) Place the metal substrate in the electroplating bath for electroplating; use the metal substrate as the cathode, a graphite plate as the anode, the distance between the cathode and the anode is 15 cm, and the current density is 10 A / cm 2 , the temperature of the electroplating bath is 50 °C, and the electroplating time is 30 min.

[0058] (4) After electroplating, wash and dry the metal substrate.

[0059] Example 3

[0060] A method for preparing a CdZr alloy coating on a metal surface, characterized by comprising the following steps:

[0061] (1) Pretreatment of the metal substrate: Grind the metal substrate, remove rust with an acidic solution, sandblast, degrease, and ultrasonically clean with deionized water, and heat to 45 °C after drying.

[0062] (2) Preparation of electroplating bath: Place a portion of water in a container, heat it to 35 °C, and add 0.25 g of cetyltrimethylammonium bromide and 0.25 g of ionic complex macromolecular surfactant respectively during stirring. Subsequently, add 0.5 g of TiC particles with a particle size of 300 nm, and continuously stir for 2 min to make it disperse evenly; Add cadmium sulfate calculated according to 65 g of cadmium ions, zirconium sulfate calculated according to 8 g of zirconium ions, 15 g of sodium aminosulfonate, 20 g of cyclohexanediaminetetraacetic acid, and 0.02 g of 2-mercaptobenzimidazole in the remaining water (total 1 L) in sequence. After stirring evenly, add the dispersion prepared previously, and add a pH regulator during continuous stirring to adjust the pH value of the electroplating bath to 5 with dilute sulfuric acid, thus obtaining the electroplating bath;

[0063] (3) Place the metal substrate in the electroplating bath for electroplating; Use the metal substrate as the cathode, the graphite plate as the anode, the distance between the cathode and the anode is 15 cm, and the current density is 7 A / cm 2 , the temperature of the electroplating bath is 45 °C, and the electroplating time is 20 min.

[0064] (4) After electroplating, wash and dry the metal substrate.

[0065] To illustrate the influence of the components of the electroplating bath of the present invention on the coating, we selected common EDTA as a complexing agent for comparison.

[0066] Comparative Example 1

[0067] The preparation steps of Comparative Example 1 are the same as those of Example 1, the difference being that WC particles are not added to the electroplating bath.

[0068] Comparative Example 2

[0069] The preparation steps of Comparative Example 2 are the same as those of Example 3, the difference being that EDTA is used to replace cyclohexanediaminetetraacetic acid in the electroplating bath.

[0070] Comparative Example 3

[0071] The preparation steps of Comparative Example 3 are the same as those of Example 3, the difference being that a single surfactant, cetyltrimethylammonium bromide, is used in the electroplating bath, and the ionic complex macromolecular surfactant is not added.

[0072] By observing the dispersion solutions configured in Examples 1-3 and Comparative Examples 1-3, the inventor found that there was a small amount of agglomeration in the dispersion solution of Comparative Example 3. This indicates that to a certain extent, the single cetyltrimethylammonium bromide surfactant has an unsatisfactory dispersion effect on nanoparticles. However, by using the binary component of cetyltrimethylammonium bromide and the ionic complex macromolecular surfactant of the present invention, a dispersion liquid with uniform dispersion and good stability can be obtained, which is beneficial to the dispersion of nanoparticles in the electroplating bath and can improve the uniformity of their distribution in the CdZr alloy coating.

[0073] Next, the thickness of the coating was measured; the composition of the coating was detected by chemical analysis methods; the hardness of the alloy coating was measured using a Vickers microhardness tester with a load of 200 g and a loading time of 30 s; the friction coefficient was measured using a friction and wear testing machine; the experimental results were recorded in Table 1.

[0074] Table 1

[0075]

[0076] From the comparison of the above data results, it can be seen that:

[0077] 1. When no nanoparticles are added to the electroplating bath, the microhardness of the alloy coating is significantly reduced and the friction coefficient increases. This indicates that the nanoparticles added in the present invention can effectively improve the hardness of the coating and enhance the wear resistance of the coating.

[0078] 2. According to Examples 1-3, to a certain extent, the higher the Cd content in the coating, the higher the microhardness, indicating that the Cd content is beneficial to the improvement of the coating hardness.

[0079] 3. In the case of not containing the ionic complex macromolecular surfactant, the prepared coating has worse friction performance because the nanoparticles are unevenly distributed in the bath and agglomerate, resulting in uneven distribution of nanoparticles in the coating and causing the surface morphology of the coating to be uneven, leading to an increase in the friction coefficient.

[0080] 4. When using EDTA instead of cyclohexanediaminetetraacetic acid as the complexing agent, the coating is inferior to the technical solution of the present invention in terms of microhardness and friction performance. This indicates that the choice of complexing agent also has a great impact on the coating performance to a large extent.

[0081] The neutral salt spray test was carried out in accordance with GB / T 10125–1997 "Artificial Atmosphere Corrosion Test Salt Spray Test", and the test results were recorded in Table 2.

[0082] Table 2

[0083] Time (h) Example 1 2762 Example 2 3120 Example 3 2896 Comparative Example 1 2179 Comparative Example 2 2686 Comparative Example 3 2517

[0084] From the data in Table 2, it can be seen that the CdZr alloy coating prepared by the present invention has excellent corrosion resistance; the nanoparticles are also beneficial to improving the overall corrosion resistance. When EDTA is used to replace cyclohexanediaminetetraacetic acid as the complexing agent, the corrosion resistance decreases, and the decrease of the coating prepared with a single surfactant cetyltrimethylammonium bromide is more obvious. This is because the distribution of nanoparticles in the coating is uneven, resulting in differences in the corrosion potential of the coating, making it more prone to corrosion.

[0085] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electroplating bath for CdZr alloy coating on a metal surface, characterized in that, it comprises the following components: cadmium ions 50 - 80 g / L; zirconium ions 5 - 10 g / L; sodium sulfamate 10 - 20 g / L; cyclohexanediaminetetraacetic acid 15 - 30 g / L; 2-mercaptobenzimidazole 0.01 - 0.05 g / L; reinforcing nanoparticles 0.1 - 0.7 g / L; cetyltrimethylammonium bromide 0.01 - 0.05 g / L; ionic complex macromolecular surfactant 0.01 - 0.05 g / L; pH regulator 5 - 25 g / L; the balance is water; the pH of the electroplating bath is 4 - 6.

2. The electroplating bath for CdZr alloy coating on a metal surface according to claim 1, characterized in that, the metal substrate is steel, aluminum or magnesium.

3. The electroplating bath for CdZr alloy coating on a metal surface according to any one of claims 1 - 2, characterized in that, the cadmium ions are selected from one or more of cadmium sulfate and cadmium chloride.

4. The electroplating bath for CdZr alloy coating on a metal surface according to any one of claims 1 - 2, characterized in that, the zirconium ions are selected from one or more of zirconium sulfate and zirconium chloride.

5. The electroplating bath for CdZr alloy coating on a metal surface according to any one of claims 1 - 2, characterized in that, the reinforcing nanoparticles are selected from one or more of WC and TiC; the particle size of the reinforcing nanoparticles is 100 - 500 nm.

6. The electroplating bath for CdZr alloy coating on a metal surface according to any one of claims 1 - 2, characterized in that, the pH regulator is selected from one or more of hydrochloric acid and sulfuric acid.

7. The electroplating bath for CdZr alloy coating on a metal surface according to any one of claims 1 - 2, characterized in that, it comprises the following components: cadmium ions 60 - 70 g / L; zirconium ions 7 - 8 g / L; sodium sulfamate 13 - 17 g / L; cyclohexanediaminetetraacetic acid 20 - 25 g / L; 2-mercaptobenzimidazole 0.02 - 0.03 g / L; reinforcing nanoparticles 0.3 - 0.5 g / L; cetyltrimethylammonium bromide 0.02 - 0.03 g / L; ionic complex macromolecular surfactant 0.02 - 0.03 g / L; pH regulator 10 - 20 g / L; the balance is water; the pH of the electroplating bath is 4.5 - 5.

5.

8. A method for preparing a CdZr alloy coating on a metal surface, characterized in that, it comprises the following steps: (1) Pretreatment of the metal substrate: The metal substrate is polished, descaled with an acidic solution, sandblasted, degreased and ultrasonically cleaned with deionized water, and then heated to 40 - 50 °C after drying; (2) Prepare the electroplating bath according to any one of claims 1 to 7: Place a part of water in a container, heat it to 30 - 40 °C, add cetyltrimethylammonium bromide and an ionic complex macromolecular surfactant respectively during stirring, then add reinforcing particles, and continuously stir for 1 - 3 min to make them disperse evenly; sequentially add cadmium ions, zirconium ions, sodium aminosulfonate, cyclohexanediaminetetraacetic acid, and 2-mercaptobenzimidazole to the remaining water, add the dispersion prepared previously after stirring evenly, and add a pH regulator to adjust the pH value of the electroplating bath during continuous stirring to obtain the electroplating bath; (3) Place the metal substrate in an electroplating bath for electroplating; (4) After electroplating, wash and dry the metal substrate.

9. The method for preparing a CdZr alloy coating on a metal surface according to claim 8, wherein, In step (3), a metal substrate serves as the cathode, a graphite plate serves as the anode, the distance between the cathode and the anode is 10 to 15 cm, and the current density is 5 to 10 A / cm 2 , the temperature of the electroplating bath is 40 to 50 °C, and the electroplating time is 10 to 30 min.

10. A CdZr alloy coating on a metal surface, prepared by the preparation method according to any one of claims 8 to 9, wherein the Cd content in the CdZr alloy coating is 70 - 80 wt.%, the Zr content is 20 - 30 wt.%, the content of reinforcing particles is 0.7 - 1.5 wt.%, and the thickness of the CdZr alloy coating is 5 - 18 μm.

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