A trivalent chromium passivation agent for galvanized zinc which can replace hexavalent chromium color passivation and a preparation method thereof

Abstract

The application discloses a trivalent chromium passivation agent for galvanized zinc which can replace hexavalent chromium color passivation, and a preparation method thereof. The trivalent chromium passivation agent comprises the following components in parts by weight: 80-120 parts of trivalent chromium salt; 10-20 parts of other metal salt; 5-10 parts of color adjusting agent; 30-40 parts of oxidizing agent; 10-20 parts of film forming promoter; 10-20 parts of complexing agent; 1-5 parts of wetting agent; 1-5 parts of inhibitor; and a certain amount of deionized water. The color adjusting agent obtained by compounding dimethyl selenium, strontium oxalate and titanium tellurate is added in the trivalent chromium passivation agent for galvanized zinc, and selenium, strontium, tellurium, titanium and other substances in the color adjusting agent are filled in the skeleton of the passivation film, so that the absorption, reflection and diffuse reflection of the passivation film to incident light are changed, thereby achieving the purpose of adjusting the color of the passivation film. The galvanized zinc part treated by the trivalent chromium passivation agent has a bright passivation film color which is almost consistent with that of the hexavalent chromium color passivation.

Description

Technical Field

[0001] This invention relates to the field of trivalent chromium color passivation technology, specifically to a zinc-plating trivalent chromium passivating agent whose passivation film color can replace hexavalent chromium color passivation and its preparation method. Background Technology

[0002] RoHS, short for "Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment," officially came into effect on July 1, 2006. Its purpose is to eliminate six substances—lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBBBs), and polybrominated diphenyl ethers (PBDEs)—from electrical and electronic products, making them more beneficial to human health and the environment. On February 18, 2006, my country, led by the Ministry of Information Industry, also issued corresponding regulations, which began regulating these six hazardous substances in electronic and electrical equipment on the market from March 1, 2007.

[0003] However, many electronic and electrical devices on the market currently require electroplating with zinc to form a passivation film on the surface. This passivation film enhances the corrosion resistance of electronic and electrical devices. In order to reduce the use of harmful hexavalent chromium, most mainstream passivating agents are formulated with trivalent chromium instead of hexavalent chromium. However, the passivated parts treated with existing trivalent chromium colored passivating agents have a bluish-green and pale color, which is far from achieving the bright passivation film color effect of hexavalent chromium colored passivation. In the process of switching from hexavalent chromium passivation to trivalent chromium passivation, some customers are accustomed to the bright color of hexavalent chromium passivation and cannot accept the bluish-green and pale color of trivalent chromium passivation. As a result, existing trivalent chromium colored passivating agents cannot meet customers' needs for passivation film color.

[0004] Therefore, it is necessary to develop a zinc-plating trivalent chromium passivating agent whose passivation film color is close to that of hexavalent chromium passivation. Summary of the Invention

[0005] The purpose of this invention is to provide a zinc plating trivalent chromium passivating agent and its preparation method that can replace hexavalent chromium color passivation with passivation film color, so as to overcome the shortcomings in the prior art.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On the one hand, a zinc plating trivalent chromium passivating agent is provided, whose passivation film color can replace hexavalent chromium color passivation, comprising the following components by weight:

[0008]

[0009]

[0010] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the trivalent chromium salt is one or more of chromium methanesulfonate, chromium sulfate, chromium nitrate, chromium chloride, and chromium bromide hexahydrate.

[0011] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium passivation with passivation film color, the other metal salts are one or more of nickel sulfate, cobalt sulfate, and cerium nitrate.

[0012] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium passivation with passivation film color, the color modifier is a compound prepared by dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0013] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the oxidant is one or more of sodium nitrate, potassium nitrate, and nitric acid.

[0014] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the film-forming promoter is one or more of sulfuric acid and sodium sulfate.

[0015] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the complexing agent is one or more of citric acid, malonic acid, ammonium bifluoride, sodium fluoride, and potassium sodium tartrate.

[0016] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the wetting agent is one or more of alkylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether.

[0017] As a preferred option for zinc plating trivalent chromium passivating agents that can replace hexavalent chromium color passivation with passivation film color, the inhibitor is one or more of sodium sulfite, sodium bisulfite, and thiourea dioxide.

[0018] On the other hand, a method for preparing a zinc plating trivalent chromium passivating agent whose passivation film color can replace hexavalent chromium passivation is provided, comprising the following steps:

[0019] S10. Add some deionized water to container A and heat it to 80-85℃;

[0020] S20. Add trivalent chromium salt to container A and stir thoroughly until completely dissolved;

[0021] S30. Add other metal salts and oxidizing agents to container A in sequence, keep warm at 80-85℃, and stir for 60 minutes.

[0022] S40. After cooling the solution from step S30 to 35-45°C, add the color adjuster to container A and stir thoroughly.

[0023] S50. Add the film-forming accelerator, complexing agent and wetting agent to container A in sequence, and stir thoroughly.

[0024] S60. Add some deionized water and inhibitor to container B, and stir thoroughly until completely dissolved;

[0025] S70. Add the solution from container B to container A, add deionized water, and stir until homogeneous to obtain the zinc plating trivalent chromium passivating agent.

[0026] The beneficial effects of this invention are:

[0027] This invention incorporates a color adjuster, a compound of dimethyl selenide, strontium oxalate, and titanium tellurate, into the trivalent chromium passivating agent for zinc plating. The selenium, strontium, tellurium, and titanium in the color adjuster fill the framework of the passivation film, altering its absorption, reflection, and diffuse reflection of incident light, thereby adjusting the color of the passivation film. The passivation film of zinc-plated parts treated with this trivalent chromium passivating agent exhibits a vibrant orange-red color (light wavelength 615-625nm), almost identical to the vibrant orange-red color (light wavelength 613-625nm) of the passivation film exhibited by hexavalent chromium colored passivation. This trivalent chromium passivating agent can completely replace hexavalent chromium colored passivation, reducing the use of highly polluting and carcinogenic hexavalent chromium while solving the problem of existing trivalent chromium colored passivation films having a bluish-green tint and a pale color (light wavelength 490-510nm), thus meeting customer demands for passivation film color. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0029] Figure 1 This is a color comparison diagram of zinc-plated parts prepared with passivating agents according to Embodiment 1 and Comparative Examples 1-2 of the present invention. Detailed Implementation

[0030] To better illustrate the objectives, technical solutions, and advantages of this invention, the following embodiments are provided. Obviously, the following embodiments are only a part of the embodiments of this invention, and not all of them; it should be understood that the embodiments of this invention are only used to illustrate the technical effects of this invention, and not to limit the scope of protection of this invention.

[0031] All raw materials used in the examples are commercially available; unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0032] Example 1:

[0033] The preparation method of the zinc-plating trivalent chromium passivating agent, in which the passivation film color can replace hexavalent chromium color passivation, in this embodiment is as follows:

[0034] 1. Weigh each raw material according to the following weight proportions:

[0035]

[0036]

[0037] The color adjuster is prepared by compounding dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0038] 2. Add 0.5L of deionized water to container A with a capacity of 1L, and heat to 80-85℃;

[0039] 3. Add 100 grams of chromium methanesulfonate to container A and stir thoroughly until completely dissolved;

[0040] 4. Add 13 grams of nickel sulfate and 35 grams of sodium nitrate to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes;

[0041] 5. After cooling the solution from step 4 to 35-45℃, add 7.5 grams of color adjuster to container A and stir thoroughly;

[0042] 6. Add 15 grams of sodium sulfate, 12 grams of ammonium bifluoride and 2 grams of polyoxyethylene fatty alcohol ether to container A in sequence, and stir thoroughly;

[0043] 7. Add 0.05-0.1L of deionized water and 2g of sodium sulfite to container B with a capacity of 0.2L, and stir thoroughly until completely dissolved;

[0044] 8. Add the solution from container B to container A, and add deionized water to 1L. Stir well to obtain the zinc plating trivalent chromium passivating agent.

[0045] Example 2:

[0046] The preparation method of the zinc-plating trivalent chromium passivating agent, in which the passivation film color can replace hexavalent chromium color passivation, in this embodiment is as follows:

[0047] 1. Weigh each raw material according to the following weight proportions:

[0048]

[0049] The color adjuster is prepared by compounding dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0050] 2. Add 0.5L of deionized water to container A with a capacity of 1L, and heat to 80-85℃;

[0051] 3. Add 95 grams of chromium sulfate to container A and stir thoroughly until completely dissolved;

[0052] 4. Add 13 grams of cobalt sulfate and 30 grams of sodium nitrate to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes;

[0053] 5. After cooling the solution from step 4 to 35-45℃, add 5 grams of color adjuster to container A and stir thoroughly;

[0054] 6. Add 20g sodium sulfate, 13g citric acid and 2g alkylphenol polyoxyethylene ether to container A in sequence, and stir thoroughly;

[0055] 7. Add 0.05-0.1L of deionized water and 5g of sodium bisulfite to container B with a capacity of 0.2L, and stir thoroughly until completely dissolved;

[0056] 8. Add the solution from container B to container A, and add deionized water to 1L. Stir well to obtain the zinc plating trivalent chromium passivating agent.

[0057] Example 3:

[0058] The preparation method of the zinc-plating trivalent chromium passivating agent, in which the passivation film color can replace hexavalent chromium color passivation, in this embodiment is as follows:

[0059] 1. Weigh each raw material according to the following weight proportions:

[0060]

[0061] The color adjuster is prepared by compounding dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0062] 2. Add 0.5L of deionized water to container A with a capacity of 1L, and heat to 80-85℃;

[0063] 3. Add 90 grams of chromium nitrate to container A and stir thoroughly until completely dissolved;

[0064] 4. Add 10 grams of cerium nitrate and 30 grams of potassium nitrate to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes;

[0065] 5. After cooling the solution from step 4 to 35-45℃, add 7.5 grams of color adjuster to container A and stir thoroughly;

[0066] 6. Add 10 grams of sulfuric acid, 15 grams of sodium fluoride and 3 grams of alkylphenol polyoxyethylene ether to container A in sequence, and stir thoroughly;

[0067] 7. Add 0.05-0.1L of deionized water and 1 gram of sodium bisulfite to container B with a capacity of 0.2L, and stir thoroughly until completely dissolved;

[0068] 8. Add the solution from container B to container A, and add deionized water to 1L. Stir well to obtain the zinc plating trivalent chromium passivating agent.

[0069] Example 4:

[0070] The preparation method of the zinc-plating trivalent chromium passivating agent, in which the passivation film color can replace hexavalent chromium color passivation, in this embodiment is as follows:

[0071] 1. Weigh each raw material according to the following weight proportions:

[0072]

[0073] The color adjuster is prepared by compounding dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0074] 2. Add 0.5L of deionized water to container A with a capacity of 1L, and heat to 80-85℃;

[0075] 3. Add 80 grams of chromium chloride to container A and stir thoroughly until completely dissolved;

[0076] 4. Add 20 grams of cerium nitrate and 35 grams of nitric acid to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes;

[0077] 5. After cooling the solution from step 4 to 35-45℃, add 10 grams of color adjuster to container A and stir thoroughly;

[0078] 6. Add 10 grams of sulfuric acid, 10 grams of potassium sodium tartrate, and 1 gram of polyoxyethylene fatty alcohol ether to container A in sequence, and stir thoroughly;

[0079] 7. Add 0.05-0.1L of deionized water and 3g of thiourea dioxide to container B with a capacity of 0.2L, and stir thoroughly until completely dissolved;

[0080] 8. Add the solution from container B to container A, and add deionized water to 1L. Stir well to obtain the zinc plating trivalent chromium passivating agent.

[0081] Example 5:

[0082] The preparation method of the zinc-plating trivalent chromium passivating agent, in which the passivation film color can replace hexavalent chromium color passivation, in this embodiment is as follows:

[0083] 1. Weigh each raw material according to the following weight proportions:

[0084]

[0085]

[0086] The color adjuster is prepared by compounding dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:4.

[0087] 2. Add 0.5L of deionized water to container A with a capacity of 1L, and heat to 80-85℃;

[0088] 3. Add 120 grams of chromium bromide hexahydrate to container A and stir thoroughly until completely dissolved;

[0089] 4. Add 15 grams of nickel sulfate and 40 grams of potassium nitrate to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes;

[0090] 5. After cooling the solution from step 4 to 35-45℃, add 8 grams of color adjuster to container A and stir thoroughly;

[0091] 6. Add 15 grams of sodium sulfate, 20 grams of malonic acid and 5 grams of alkylphenol polyoxyethylene ether to container A in sequence, and stir thoroughly;

[0092] 7. Add 0.05-0.1L of deionized water and 3g of thiourea dioxide to container B with a capacity of 0.2L, and stir thoroughly until completely dissolved;

[0093] 8. Add the solution from container B to container A, and add deionized water to 1L. Stir well to obtain the zinc plating trivalent chromium passivating agent.

[0094] Test example:

[0095] Commercially available hexavalent chromium passivating agent and commercially available trivalent chromium passivating agent were used as Comparative Example 1 and Comparative Example 2, respectively. The zinc-plated parts were passivated using the zinc-plating trivalent chromium passivating agent prepared in Examples 1-5 and the commercially available passivating agent in Comparative Examples 1-2. First, the pH value of the passivating agents in Examples 1-5 and Comparative Examples 1-2 was adjusted to 1.8-2.2. Then, at a temperature of 20-30℃, the zinc-plated parts were immersed in the solutions of each passivating agent for 25 seconds. After passivation, the zinc-plated parts were removed and sequentially washed with water and dried with hot air. Finally, they were left to stand naturally, and the changes in the appearance and color of the passivation film were continuously observed. The specific test results are as follows:

[0096] Reference manual attached Figure 1 , Figure 1 From left to right, the zinc-plated parts obtained in Example 1, Comparative Example 1, and Comparative Example 2 are shown in the figures. It can be clearly seen from the figures that the passivation film of the zinc-plated part treated with the trivalent chromium passivating agent of Example 1 (left figure) is a bright orange-red color, which is almost the same as the passivation film color of the hexavalent chromium passivating agent of Comparative Example 1 (in the figure). However, the passivation film of the zinc-plated part treated with a commercially available trivalent chromium passivating agent of Comparative Example 2 (right figure) is bluish-green and light, and cannot achieve the bright passivation film color effect of the hexavalent chromium passivating agent.

[0097] As shown in Table 1 below, the passivation film color wavelength of the zinc plating treated with the trivalent chromium passivating agent of Examples 1-5 of the present invention is always maintained in the range of 615-625nm, while the color wavelength of the hexavalent chromium passivating agent of Comparative Example 1 is also maintained in the range of 613-625nm. The wavelengths of the passivation film of Examples 1-5 and Comparative Example 1 are almost consistent. This further demonstrates that the color of the passivation film of the zinc plating treated with the trivalent chromium passivating agent of the present invention is consistent with the color of the passivation film of the hexavalent chromium passivating agent of Comparative Example 1. However, the passivation film color of the zinc plating treated with a commercially available trivalent chromium passivating agent of Comparative Example 2 is always maintained in the range of 490-510nm, which is far different from the wavelength of the passivation film color of the zinc plating obtained in Examples 1-5 and Comparative Example 1. This further demonstrates that the passivation film color of the zinc plating treated with a commercially available trivalent chromium passivating agent of Comparative Example 2 is bluish-green and pale, and cannot obtain the bright passivation film color effect of hexavalent chromium passivating agent.

[0098] Meanwhile, the light wavelength of the galvanized parts treated with the trivalent chromium passivating agent of the present invention did not change significantly after being left for a long time. This shows that the passivation effect of the trivalent chromium passivating agent of the present invention has excellent stability and can completely replace hexavalent chromium passivation. The trivalent chromium passivating agent of the present invention not only reduces the use of hexavalent chromium, which is highly polluting and carcinogenic, but also solves the problem of the light color of the existing trivalent chromium passivation film, and can meet the customer's needs for the color of the passivation film.

[0099] Table 1. Comparison of light wavelengths corresponding to the colors of passivated zinc-plated parts in Examples 1-5 and Comparative Examples 1-2.

[0100] Placement time Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 1 day 625nm 625nm 625nm 624nm 625nm 625nm 510nm 3 days 625nm 624nm 624nm 624nm 623nm 623nm 506nm 5 days 624nm 624nm 623nm 623nm 623nm 623nm 504nm 7 days 624nm 623nm 622nm 623nm 622nm 622nm 502nm 15 days 622nm 622nm 621nm 622nm 621nm 621nm 498nm 1 month 621nm 620nm 621nm 620nm 620nm 618nm 495nm 2 months 619nm 618nm 619nm 618nm 617nm 616nm 493nm 3 months 616nm 615nm 616nm 616nm 615nm 613nm 490nm

[0101] It should be stated that the above-described specific embodiments are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art should understand that various modifications, equivalent substitutions, and variations can be made to the present invention. However, such variations, as long as they do not depart from the spirit of the present invention, should be within the scope of protection of the present invention. Furthermore, some terminology used in this specification and claims is not limiting, but merely for ease of description.

Claims

1. A zinc plating trivalent chromium passivating agent whose passivation film color can replace hexavalent chromium passivation, characterized in that, Each liter of zinc plating trivalent chromium passivating agent contains the following components: Trivalent chromium salts: 80-120 g / L; Other metal salts: 10-20 g / L; Color adjuster 5-10g / L; Oxidizing agent 30-40 g / L; Film-forming accelerator 10-20 g / L; Complexing agent 10-20 g / L; Wetting agent 1-5g / L; Inhibitor 1-5g / L; Deionized water balance; The trivalent chromium salt is one or more of chromium methanesulfonate, chromium sulfate, chromium nitrate, chromium chloride, and chromium bromide hexahydrate; The other metal salts are one or more of nickel sulfate, cobalt sulfate, and cerium nitrate; The color adjuster is a compound prepared by mixing dimethyl selenide, strontium oxalate and titanium tellurate in a weight ratio of 2:1.5:

4. The oxidant is one or more of sodium nitrate, potassium nitrate, and nitric acid; The film-forming promoter is one or more of sulfuric acid and sodium sulfate; The complexing agent is one or more of citric acid, malonic acid, ammonium bifluoride, sodium fluoride, and potassium sodium tartrate. The wetting agent is one or more of alkylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether; The inhibitor is one or more of sodium sulfite, sodium bisulfite, and thiourea dioxide.

2. A method for preparing a zinc plating trivalent chromium passivating agent whose passivation film color can replace hexavalent chromium passivation as described in claim 1, characterized in that, Includes the following steps: S10. Add some deionized water to container A and heat it to 80-85℃; S20. Add trivalent chromium salt to container A and stir thoroughly until completely dissolved; S30. Add other metal salts and oxidizing agents to container A in sequence, keep warm at 80-85℃ and stir for 60 minutes. S40. After cooling the solution from step S30 to 35-45°C, add the color adjuster to container A and stir thoroughly. S50. Add the film-forming accelerator, complexing agent and wetting agent to container A in sequence, and stir thoroughly. S60. Add some deionized water and inhibitor to container B, and stir thoroughly until completely dissolved; S70. Add the solution from container B to container A, add deionized water, and stir until homogeneous to obtain the zinc plating trivalent chromium passivating agent.

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