Electroplated layer protective agent and preparation method thereof

Abstract

The invention relates to an electroplated coating protective agent and a preparation method thereof, and belongs to the technical field of electroplated coating protective agents, and the protective agent comprises the following raw materials: main salt, auxiliary salt, a composite complexing agent, 1-docosanethiol, a sealing agent, absolute ethyl alcohol and deionized water. The succinic acid, the N-sodium lauroyl sarcosinate and the citrazinic acid are used as the composite complexing agent, and starting from different aspects of activating the surface of the coating, accelerating the growth of the protective film layer and increasing the compactness of the protective film layer, the prepared protective agent can effectively improve the corrosion resistance effect of the coating; and the added 1-docosanethiol is used for reducing the defect area of the protective film layer and further effectively improving the corrosion resistance of the protective film. Besides, chromic nitrate is used as a main salt, cerous sulfate and sodium molybdate are used as auxiliary salts, and sodium silicate is used as a sealing agent, so that the prepared protective agent can effectively have remarkable salt spray resistance, and meanwhile, the appearance quality of a formed film layer can also be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of protective agents for electroplating layers, and in particular relates to an electroplating layer protective agent and a preparation method thereof. Background Art

[0002] In modern industrial production, electroplating, as an important means of improving the surface properties of metal materials, is widely used in numerous fields, including machinery manufacturing, electronics, and automotive parts. Electroplating not only imparts a decorative appearance to metal surfaces but also significantly improves their corrosion resistance, wear resistance, and hardness. However, electroplating is susceptible to environmental erosion during actual use, leading to oxidation, corrosion, and discoloration, which can affect the product's service life and appearance. Therefore, the use of electroplating protective agents is crucial for protecting the electroplating layer.

[0003] Currently, there are many types of electroplating protective agents on the market, but they generally have some shortcomings. Among them, the most prominent one is that many traditional protective agents are difficult to effectively resist the erosion of corrosive media in harsh corrosive environments, such as industrial atmospheric environments or high-humidity, high-salinity marine environments, resulting in rapid corrosion, discoloration, blistering, and other phenomena in the electroplating layer, resulting in poor corrosion resistance. On the other hand, in accelerated corrosion tests such as salt spray tests that simulate actual use environments, the electroplating layer treated with existing protective agents often fails to achieve the ideal salt spray resistance. After the salt spray test, obvious corrosion products will appear on the surface of the electroplating layer, affecting the appearance and performance of the product. In addition, while some protective agents improve corrosion resistance and salt spray resistance, they also sacrifice the product's appearance quality, resulting in uneven film formation, darkening, and poor gloss loss. These problems seriously affect the product's appearance quality and cannot meet the strict appearance requirements of the high-end manufacturing field. Therefore, in order to address the problems existing in existing electroplating protective agents in terms of corrosion resistance, salt spray resistance, and appearance quality, it is urgent to provide a new electroplating protective agent and its preparation method. Summary of the Invention

[0004] The purpose of the present invention is to provide an electroplating layer protective agent and a preparation method thereof, which solves the problems of poor corrosion resistance and salt spray resistance existing in existing electroplating layer protective agents and can also improve the appearance quality of the product.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An electroplating layer protective agent includes the following raw materials:

[0007] Main salt, auxiliary salt, complex complexing agent, 1-docosanthiol;

[0008] The main salt includes chromium nitrate;

[0009] The auxiliary salt includes cerous sulfate and sodium molybdate;

[0010] The composite complexing agent comprises succinic acid, sodium N-lauroyl sarcosinate and citrazinic acid.

[0011] As a preferred technical solution of the present invention, each liter of electroplating layer protective agent includes the following raw materials by mass:

[0012] Main salt 10-30g, auxiliary salt 55-70g, composite complexing agent 7.1-10.12g, 1-docosanthiol 0.2-0.3g.

[0013] As a preferred technical solution of the present invention, the auxiliary salt includes 45-55g of cerous sulfate and 15-20g of sodium molybdate.

[0014] As a preferred technical solution of the present invention, the composite complexing agent includes 4-5g of succinic acid, 0.1-0.12g of sodium N-lauroyl sarcosinate, and 2-3g of citrazinic acid.

[0015] As a preferred technical solution of the present invention, the electroplating layer protective agent also includes a sealing agent, anhydrous ethanol and deionized water.

[0016] As a preferred technical solution of the present invention, each liter of electroplating layer protective agent further includes the following components by mass:

[0017] 2-4g sealing agent, 5-10g anhydrous ethanol, and the balance deionized water.

[0018] As a preferred technical solution of the present invention, the sealing agent includes sodium silicate.

[0019] A method for preparing an electroplating layer protective agent specifically comprises the following steps:

[0020] S1. Stirring the main salt, auxiliary salt and deionized water under controlled temperature to obtain a mixture A;

[0021] S2. Add 1-docosanthiol, a complexing agent, and a blocking agent to anhydrous ethanol in sequence, and control the temperature while stirring to obtain a mixture B;

[0022] S3. Add mixture A to mixture B under stirring, adjust the pH, and allow to stand for aging to obtain a protective agent.

[0023] As a preferred technical solution of the present invention, the temperature of the temperature control in step S1 is 50-55° C., and the stirring time is 0.5-1 h.

[0024] As a preferred technical solution of the present invention, the temperature of the temperature-controlled stirring in step S2 is 60-70° C. and the time is 10-15 minutes.

[0025] As a preferred technical solution of the present invention, the pH adjustment in step S3 is specifically to use nitric acid solution or sodium hydroxide solution to adjust the pH to 1.8-2.2; and the aging time is 24 hours.

[0026] Furthermore, the mass concentration of the nitric acid solution is 5%, and the mass concentration of the sodium hydroxide solution is 10%.

[0027] Beneficial effects of the present invention:

[0028] (1) The present application solves the technical problem that a single complexing agent only has a good effect in a certain aspect but has poor overall performance. Therefore, the present application starts from different aspects of activating the coating surface, accelerating the growth of the protective film layer, and increasing the density of the protective film layer, and combines the action mechanism of different complexing agents to make them synergistic on the coating surface. The protective agent prepared in this way can significantly improve the corrosion resistance of the coating;

[0029] Specifically, the organic dicarboxylic acid succinic acid is used to activate the surface of the coating to accelerate the growth of the protective film on the surface of the coating. At the same time, the addition of sodium N-lauroyl sarcosine with a smaller energy level difference enhances the interaction between the system and the coating surface, effectively playing an assisting role in forming a more stable protective film. In addition, citrazinic acid is added to provide heterocyclic nitrogen atoms to participate in coordination, further enhancing the density of the protective film. Therefore, the protective agent prepared in this way can have an excellent corrosion resistance effect.

[0030] (2) 1-docosanthiol contains not only a mercapto group that has an adsorption effect on the coating but also a hydrophobic non-polar long-chain alkyl group. The addition of 1-docosanthiol can reduce the defect area of ​​the protective film layer, further improve the continuity, uniformity and flatness of the protective film, and thus effectively improve the gloss and corrosion resistance of the protective film.

[0031] (3) The present application uses chromium nitrate as a skeleton to form a network structure as a key component of film formation, uses sulfate introduced by cerous sulfate to improve the bonding strength between the protective film and the substrate, and uses sodium molybdate to fill the micropores and improve the stability of the protective film in neutral salt spray. Therefore, the protective agent system composed of chromium nitrate as the main salt, rare earth metal salt cerous sulfate and sodium molybdate as auxiliary salts has good salt spray resistance to a certain extent. However, the salt spray resistance of the protective film formed by trivalent chromium as the main salt is still slightly lacking compared to hexavalent chromium. Therefore, the present application also adds sodium silicate as a sealing agent to make the film layer more dense and complete, so that the protective agent prepared in this way has significant salt spray resistance;

[0032] In addition, the main salt and auxiliary salt compounded in the present application can also improve the flatness, uniformity and high gloss of the protective film. Specifically, the nitrate ions contained in the main salt can play a light-emitting role, while the cerous sulfate in the auxiliary salt can deepen the color of the protective film and improve the optical uniformity of the film layer. At the same time, sodium molybdate can effectively cooperate with the cerous ions to optimize the optical properties. Therefore, the protective film displayed by the protective agent prepared by the present application also has the characteristics of flatness, uniform color and high gloss, which greatly improves the appearance quality of the product and enhances the market competitiveness of the product. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Throughout the specification, unless otherwise specified, all raw materials used in the present invention can be purchased from the market; among them, sodium N-lauroyl sarcosinate, model: S8100-25, was purchased from Beijing Solebow Technology Co., Ltd.; citrazinic acid, model: 6338, was purchased from Shandong West Asia Chemical Co., Ltd.; 1-docosanthiol, model: D3905, was purchased from J&K Technology Co., Ltd.; the above will not be repeated in detail later.

[0035] Example 1

[0036] An electroplating protective agent, each liter of which comprises the following raw materials by mass:

[0037] Chromium nitrate 10g, cerous sulfate 55g, sodium molybdate 17.5g, succinic acid 4.5g, sodium N-lauroylsarcosinate 0.1g, citrazinic acid 2.5g, 1-docosanthiol 0.22g, sodium silicate 4g, anhydrous ethanol 7.5g, deionized water balance;

[0038] The preparation method of the electroplating layer protective agent specifically comprises the following steps:

[0039] S1. Stirring chromium nitrate, cerous sulfate, sodium molybdate and deionized water at a temperature of 52.5° C. to obtain a mixture A.

[0040] S2. 1-docosyl mercaptan, succinic acid, sodium N-lauroyl sarcosinate, citrazinic acid, and sodium silicate were sequentially added to anhydrous ethanol, and the mixture was stirred at 70° C. for 10 minutes to obtain a mixture B.

[0041] S3. Add mixture A to mixture B under stirring, adjust the pH to 1.9 with a 5% nitric acid solution or a 10% sodium hydroxide solution, and allow to stand for aging for 24 hours to obtain a protective agent.

[0042] Example 2

[0043] An electroplating protective agent, each liter of which comprises the following raw materials by mass:

[0044] 30g chromium nitrate, 50g cerous sulfate, 15g sodium molybdate, 4g succinic acid, 0.1g sodium N-lauroylsarcosinate, 2.2g citrazinic acid, 0.2g 1-docosanthiol, 3g sodium silicate, 5g anhydrous ethanol, and the balance deionized water;

[0045] The preparation method of the electroplating layer protective agent specifically comprises the following steps:

[0046] S1. Stir chromium nitrate, cerous sulfate, sodium molybdate and deionized water at 50° C. to obtain a mixture A.

[0047] S2. 1-docosyl mercaptan, succinic acid, sodium N-lauroyl sarcosinate, citrazinic acid, and sodium silicate were sequentially added to anhydrous ethanol, and the mixture was stirred at 60° C. for 15 minutes to obtain a mixture B.

[0048] S3. Add mixture A to mixture B under stirring, adjust the pH to 2.0 with a 5% nitric acid solution or a 10% sodium hydroxide solution, and allow to stand for aging for 24 hours to obtain a protective agent.

[0049] Example 3

[0050] An electroplating protective agent, each liter of which comprises the following raw materials by mass:

[0051] 25g chromium nitrate, 45g cerous sulfate, 16g sodium molybdate, 5g succinic acid, 0.11g sodium N-lauroylsarcosinate, 3g citrazinic acid, 0.25g 1-docosanthiol, 3.5g sodium silicate, 9g anhydrous ethanol, balance deionized water;

[0052] The preparation method of the electroplating layer protective agent specifically comprises the following steps:

[0053] S1. Stirring chromium nitrate, cerous sulfate, sodium molybdate and deionized water at 54° C. to obtain a mixture A.

[0054] S2. 1-docosyl mercaptan, succinic acid, sodium N-lauroyl sarcosinate, citrazinic acid, and sodium silicate were sequentially added to anhydrous ethanol, and the mixture was stirred at 67.5° C. for 11 minutes to obtain a mixture B.

[0055] S3. Add mixture A to mixture B under stirring, adjust the pH to 1.8 with a 5% nitric acid solution or a 10% sodium hydroxide solution, and allow to stand for aging for 24 hours to obtain a protective agent.

[0056] Example 4

[0057] An electroplating protective agent, each liter of which comprises the following raw materials by mass:

[0058] 20g chromium nitrate, 52.5g cerous sulfate, 19g sodium molybdate, 4.2g succinic acid, 0.12g sodium N-lauroylsarcosinate, 2g citrazinic acid, 0.23g 1-docosanthiol, 2g sodium silicate, 10g anhydrous ethanol, balance deionized water;

[0059] The preparation method of the electroplating layer protective agent specifically comprises the following steps:

[0060] S1. Stir chromium nitrate, cerous sulfate, sodium molybdate and deionized water at 55° C. to obtain a mixture A.

[0061] S2. 1-docosyl mercaptan, succinic acid, sodium N-lauroyl sarcosinate, citrazinic acid, and sodium silicate were sequentially added to anhydrous ethanol, and the mixture was stirred at 65° C. for 14 minutes to obtain a mixture B.

[0062] S3. Add mixture A to mixture B under stirring, adjust the pH to 2.2 with a 5% nitric acid solution or a 10% sodium hydroxide solution, and allow to stand for aging for 24 hours to obtain a protective agent.

[0063] Example 5

[0064] An electroplating protective agent, each liter of which comprises the following raw materials by mass:

[0065] 15g chromium nitrate, 47.5g cerous sulfate, 20g sodium molybdate, 4.8g succinic acid, 0.11g sodium N-lauroylsarcosinate, 2.8g citrazinic acid, 0.28g 1-docosanthiol, 2.5g sodium silicate, 6g anhydrous ethanol, and the balance deionized water;

[0066] The preparation method of the electroplating layer protective agent specifically comprises the following steps:

[0067] S1. Stir chromium nitrate, cerous sulfate, sodium molybdate and deionized water at 51° C. to obtain a mixture A.

[0068] S2. 1-docosyl mercaptan, succinic acid, sodium N-lauroyl sarcosinate, citrazinic acid, and sodium silicate were sequentially added to anhydrous ethanol, and the mixture was stirred at 62.5° C. for 12.5 min to obtain a mixture B.

[0069] S3. Add mixture A to mixture B under stirring, adjust the pH to 2.1 with a 5% nitric acid solution or a 10% sodium hydroxide solution, and allow to stand for aging for 24 hours to obtain a protective agent.

[0070] Comparative Example 1

[0071] Compared with Example 2, the difference is that in Comparative Example 1, no succinic acid is added, and the missing weight is made up with sodium N-lauroyl sarcosinate and citrazinic acid in a mass ratio of 0.1:2.2, and the other operating steps and parameters remain unchanged.

[0072] Comparative Example 2

[0073] Compared with Example 2, the difference is that in Comparative Example 2, no sodium N-lauroyl sarcosinate is added, and the missing weight is made up with succinic acid and citrazinic acid in a mass ratio of 2:1.1. The other operating steps and parameters remain unchanged.

[0074] Comparative Example 3

[0075] Compared with Example 2, the difference is that in Comparative Example 3, citrazinic acid is not added, and the missing weight is made up with succinic acid and sodium N-lauroyl sarcosinate in a mass ratio of 4:0.1, and the other operating steps and parameters remain unchanged.

[0076] Comparative Example 4

[0077] Compared with Example 2, the difference is that 1-docosanyl mercaptan is not added in Comparative Example 4, and the other operating steps and parameters remain unchanged.

[0078] Comparative Example 5

[0079] Compared with Example 2, the difference is that in Comparative Example 5, the amount of chromium nitrate added is 8 g, and the other operating steps and parameters remain unchanged.

[0080] Comparative Example 6

[0081] Compared with Example 2, the difference is that the amount of chromium nitrate added in Comparative Example 6 is 32 g, and the other operating steps and parameters remain unchanged.

[0082] Comparative Example 7

[0083] Compared with Example 2, the difference is that in Comparative Example 7, no cerous sulfate is added, the missing weight is made up with sodium molybdate, and the other operating steps and parameters remain unchanged.

[0084] Comparative Example 8

[0085] Compared with Example 2, the difference is that in Comparative Example 8, no sodium molybdate is added, the missing weight is made up with cerous sulfate, and the other operating steps and parameters remain unchanged.

[0086] Test Case

[0087] A DC51 D+Z galvanized sheet workpiece (purchased from Shanghai Zhuyuan Trading Co., Ltd.) was cut into pieces with a size of 25 mm x 50 mm x 1 mm as test pieces. The test pieces were polished, degreased, ultrasonically cleaned with deionized water for 2 minutes, immersed in the protective agents prepared in Examples 1-5 and Comparative Examples 1-8 for 30 seconds (at 30° C.), ultrasonically cleaned with deionized water at 50° C. for 2 minutes, cleaned with deionized water for 3 minutes, and dried with hot air at 80° C. The smoothness, color uniformity, and gloss of the surface film of the test pieces were observed and recorded by the same worker. The results are shown in Table 1. The following tests were also conducted:

[0088] (1) Corrosion resistance: Three different areas were circled with a marker on the surface of the test piece soaked in the protective solution prepared in Examples 1-5 and Comparative Examples 1-4. A drop of lead acetate solution (preparation method of lead acetate solution: dissolve 5 g of lead acetate in 50 mL of deionized water and dilute to 100 mL, and adjust the pH to 6.0 with acetic acid) was dropped on each area. The time for the drop to turn black was recorded and the average value was taken. The corrosion resistance of the passivation film was judged by the length of time. The results are shown in Table 1.

[0089] (2) Salt spray resistance: The test pieces immersed in the protective solutions prepared in Examples 1-5 and Comparative Examples 5-8 were tested according to the neutral salt spray test in GB / T 10125-2012. The test temperature was 35°C and the NaCl concentration was 50 g / L. The time when the white rust area of ​​the test pieces was greater than 5% was recorded. The results are shown in Table 1.

[0090] Table 1

[0091]

[0092] As can be seen from the data in Table 1 for the Examples and Comparative Examples 1-4, the protective agent prepared by the present invention exhibits excellent corrosion resistance. Specifically, this is because the present invention combines succinic acid, sodium N-lauroylsarcosinate, and citrazinic acid to activate the coating surface, accelerate the growth of the protective film, and increase the density of the protective film, respectively. This solves the technical problem that a single complexing agent only provides a good effect in a certain aspect but has poor overall performance, effectively enabling the prepared protective agent to enhance the corrosion resistance of the coating. Furthermore, the addition of 1-docosanthiol effectively enhances the corrosion resistance of the protective film by reducing the defect area of ​​the protective film.

[0093] It is not difficult to find from the data of the embodiment and comparative examples 5-8 in Table 1 that the protective agent prepared by the present invention has significant salt spray resistance and can also improve the smoothness, uniformity and high gloss of the surface appearance of the protective film.

[0094] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0095] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A protective agent for electroplating layer, characterized in that: Including the following raw materials: Main salt, auxiliary salt, complex complexing agent, 1-docosanthiol; The main salt includes chromium nitrate; The auxiliary salt includes cerous sulfate and sodium molybdate; The composite complexing agent comprises succinic acid, sodium N-lauroyl sarcosinate and citrazinic acid.

2. The electroplating layer protective agent according to claim 1, characterized in that Each liter of electroplating protective agent includes the following raw materials by mass: Main salt 10-30g, auxiliary salt 55-70g, composite complexing agent 7.1-10.12g, 1-docosanthiol 0.2-0.3g.

3. The electroplating layer protective agent according to claim 1, characterized in that The auxiliary salt includes 45-55g of cerous sulfate and 15-20g of sodium molybdate.

4. The electroplating layer protective agent according to claim 1, characterized in that The composite complexing agent comprises 4-5g of succinic acid, 0.1-0.12g of sodium N-lauroyl sarcosinate, and 2-3g of citrazinic acid.

5. The electroplating layer protective agent according to claim 1, characterized in that The electroplating layer protective agent also includes a sealing agent, anhydrous ethanol and deionized water.

6. The electroplating layer protective agent according to claim 5, characterized in that: Each liter of the electroplating layer protective agent further comprises the following components by mass: 2-4 g of sealing agent, 5-10 g of anhydrous ethanol, and the balance of deionized water.

7. The electroplating layer protective agent according to claim 5, characterized in that: The sealing agent includes sodium silicate.

8. A method for preparing the electroplating layer protective agent according to any one of claims 5 to 7, characterized in that: The specific steps include: S1. Stirring the main salt, auxiliary salt and deionized water under controlled temperature to obtain a mixture A; S2. Add 1-docosanthiol, a complexing agent, and a blocking agent to anhydrous ethanol in sequence, and control the temperature while stirring to obtain a mixture B; S3. Add mixture A to mixture B under stirring, adjust the pH, and allow to stand for aging to obtain a protective agent.

9. The electroplating layer protective agent according to claim 8, characterized in that: The temperature of the temperature control in step S1 is 50-55° C., and the stirring time is 0.5-1 h.

10. The electroplating layer protective agent according to claim 8, characterized in that: The temperature of the temperature-controlled stirring in step S2 is 60-70° C. and the time is 10-15 minutes; the pH adjustment in step S3 is specifically to adjust the pH to 1.8-2.2 using nitric acid solution or sodium hydroxide solution; and the aging time is 24 hours.

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