A silver plating water-based anti-tarnish sealant, anti-tarnish film and preparation method thereof

Abstract

The present application belongs to a kind of anti-tarnish sealant, for the technical problem that existing anti-tarnish agent can only extend the tarnish time, reduce the degree of tarnish, and the high temperature stability is poor, the silver-plated parts after treatment poor acid and salt fog ability, provide a kind of silver coating water-based anti-tarnish sealant, anti-tarnish film and its preparation method, anti-tarnish sealant includes yttrium zirconium composite sol, silane coupling agent, alkyl mercaptan, emulsifier, wetting agent, penetrant and water, it is proved to have the dual role of anti-tarnish and sealing silver coating hole, can significantly improve the anti-tarnish ability and acid and salt fog resistance of silver coating, and has very high high-temperature stability, can withstand 900 ℃ high-temperature baking.

Description

TECHNICAL FIELD

[0001] The present application belongs to a kind of anti-tarnish sealant, specifically relates to a kind of silver plating water-based anti-tarnish sealant, anti-tarnish film and preparation method thereof. BACKGROUND

[0002] Silver plating is soft, can withstand bending and impact, easy to polish, with self-lubricating performance, and has high electrical conductivity, thermal conductivity and good weldability. Therefore, it is widely used in the aviation industry, such as contact sheet, plug, plug rod, locking wire and other parts on the surface of the instrument, electrical and electronic equipment in aviation, which can enhance the electrical conductivity of these parts, reduce the surface contact resistance, and improve the welding ability of the metal. For example, the oil distribution disc, cover, plunger, seat, shaft and other parts in hydraulic accessories can reduce wear by silver plating. The bolts and nuts in the engine are plated with silver to prevent high-temperature bonding. Although silver has high chemical stability, it has poor resistance to sulfur-containing atmosphere, and is easily tarnished to brown and blue-black, which makes the appearance and electrical contact performance worse. In addition, due to the problem of electroplating process, silver plating inevitably has holes, which easily forms "large cathode, small anode" to accelerate the corrosion of metal matrix.

[0003] In preventing silver discoloration, the commonly used methods are chemical passivation, electrochemical passivation, and immersion of silver discoloration prevention agent. Among them, the use of passivation solution containing CrO3 to form a conversion film on the surface of silver layer has the advantages of simple equipment and low cost, but the anti-discoloration ability is poor, and at the same time, the silver thickness is lost by 2-3 μm; electrochemical passivation is cathodic electrolytic passivation in a solution containing K2CrO7, the film layer is dense, and the anti-discoloration ability is better than that of chemical passivation; the immersion of silver discoloration prevention agent can cover a thin and transparent organic film on the surface of silver plating layer, so as to isolate the direct contact between the silver layer and the air corrosion medium, and achieve the purpose of preventing silver discoloration. The method of immersion of silver discoloration prevention agent is simple to operate and does not lose the silver layer, and is the most widely used method at present. For example, the Chinese invention patent with the patent number ZL200710075422.5 discloses a water-soluble silver protection agent composed of linear saturated alkane mercaptan with carbon chain of 12-24, oligomer wetting agent containing hydroxyl functional group with carbon chain of not more than 12, and emulsifier. The Chinese invention patent with the patent number ZL201310374346.3 discloses a water-soluble silver protection agent composed of fatty alcohol polyoxyethylene ether, N-phenylmethyl phenylacetamide, and protective additive. The Chinese invention patent with the publication number CN106065468A discloses a protection agent for cyanide-free silver plating layer containing alkyl mercaptan compound. The Chinese invention patent with the publication number CN108193209A discloses a water-based silver plating protection agent containing octadecyl mercaptan. The Chinese invention patent with the patent number ZL201910326145.3 discloses a water-based silver protection agent, and the composition thereof is: octadecyl mercaptan 40-60 g, trimethyl mercapto phosphate 4-10 g, emulsifier 20-60 g, coupling agent 2-5 g, silicon dioxide 5-10 g, stabilizer 10-15 g, and the rest is water. In addition, DJB-823, LD-4310, HTAg-2000, and BK protection agent are also commercialized products for preventing silver discoloration. However, the above-mentioned methods can only prolong the time of silver discoloration or reduce the degree of silver discoloration, and have poor high-temperature stability, in addition, they also cannot effectively seal the pores of silver plating layer, and the silver plated parts after treatment have poor acid resistance and salt fog resistance. SUMMARY

[0004] The present application aims at the technical problems that the existing silver discoloration prevention agent can only prolong the discoloration time, reduce the discoloration degree, and has poor high-temperature stability, and the silver plated parts after treatment have poor acid resistance and salt fog resistance, and provides a water-based anti-discoloration sealing agent for silver plating layer, an anti-discoloration film, and a preparation method thereof.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] In the first aspect, the present application provides a water-based anti-discoloration sealing agent for silver plating layer, and the mass percentage of each component is as follows, based on the total mass of 100%:

[0007] Yttrium zirconium complex sol: 10-20%;

[0008] Silane coupling agent: 1-5%;

[0009] Alkyl mercaptan: 0.5-2%;

[0010] Emulsifier: 0.5-2%;

[0011] Wetting agent: 0.1-1%;

[0012] Penetrant: 0.1-1%;

[0013] Balance: water.

[0014] Preferably, the yttrium zirconium complex sol comprises Y2O3 and ZrO2; wherein the atomic ratio of Y and Zr is 1:10-1:100.

[0015] Preferably, the silane coupling agent is glycidyloxypropyltrimethoxysilane or glycidyloxypropyltriethoxysilane.

[0016] Preferably, the alkyl mercaptan is A-alkane mercaptan, wherein 12≤A≤18.

[0017] Preferably, the alkyl mercaptan is dodecyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan or octadecyl mercaptan.

[0018] Preferably, the emulsifier is Tween-60 or Tween-80;

[0019] The wetting agent is an alkyl phenol polyoxyethylene ether compound or a polyether modified dimethyl siloxane compound;

[0020] The penetrant is a fatty alcohol polyoxyethylene ether compound.

[0021] In a second aspect, the present application provides a preparation method of the above-mentioned water-based anti-tarnishing sealant for silver plating layer, comprising:

[0022] S1. Disperse zirconium carbonate hydroxide and yttrium carbonate in water, drop acetic acid under stirring, and react until the solution is transparent to obtain solution I;

[0023] S2. Mix the silane coupling agent, alkyl mercaptan, penetrant, wetting agent and emulsifier uniformly to obtain solution II;

[0024] S3. Mix solution I and solution II, and adjust the concentration by adding water. The preparation is completed after uniform mixing.

[0025] Preferably, in step S1, the molar ratio of acetic acid to zirconium is 2:1-3:1.

[0026] Preferably, in step S1, the reaction is carried out at 70-80℃.

[0027] In a third aspect, the present application provides a method for preparing a discoloration-resistant film, comprising:

[0028] The water-based discoloration-resistant sealing agent for silver plating is diluted.

[0029] The part with the silver plating on the surface is immersed in the diluted sealing agent, or the diluted sealing agent is coated on the part with the silver plating on the surface, so as to form a discoloration-resistant film on the surface of the silver plating.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] The present application provides a water-based discoloration-resistant sealing agent for silver plating, which comprises yttrium-zirconium composite sol, silane coupling agent, alkyl mercaptan, emulsifier, wetting agent, penetrating agent and water. It has been verified that the sealing agent has the dual functions of preventing silver discoloration and sealing the pores of silver plating, can significantly improve the discoloration resistance and acid salt mist resistance of silver plating, and has high high-temperature stability and can withstand 900℃ high-temperature baking.

[0032] The present application also provides a method for preparing a water-based discoloration-resistant sealing agent for silver plating, which can obtain the above sealing agent, has simple operation steps, is easy to implement and is convenient for industrial promotion. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application.

[0034] Therefore, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] In view of the problems of insufficient discoloration resistance, poor high-temperature stability and poor acid and salt mist resistance of existing silver discoloration-resistant agents, the present application provides a water-based discoloration-resistant sealing agent for silver plating, a method for preparing a water-based discoloration-resistant sealing agent for silver plating, and a method for preparing a discoloration-resistant film.

[0036] The method for preparing a water-based discoloration-resistant sealing agent for silver plating can comprise the following steps:

[0037] S101, dispersing zirconium carbonate hydroxide and yttrium carbonate in water, adding acetic acid dropwise under stirring, and reacting until the solution is transparent to obtain solution I.

[0038] S102, the silane coupling agent, alkyl mercaptan, penetrant, wetting agent and emulsifier are mixed uniformly to obtain solution II.

[0039] S103, solution I and solution II are mixed, and water is added to adjust the concentration. After uniform mixing, the preparation is completed.

[0040] Through the above reaction steps, the water-based anti-tarnish sealant for silver plating layer can be obtained, which has the following composition:

[0041] The mass percentage of each component is as follows, based on the total mass of 100%: yttrium-zirconium composite sol: 10-20%; silane coupling agent: 1%-5%; alkyl mercaptan: 0.5%-2%; emulsifier: 0.5%-2%; wetting agent: 0.1%-1%; penetrant: 0.1%-1%; and the balance: water.

[0042] The application will be further described in detail below with reference to examples:

[0043] Example 1

[0044] (1) 3.08 kg of zirconium carbonate and 0.036 kg of yttrium carbonate were weighed and added to 5 kg of water to disperse the zirconium carbonate and yttrium carbonate in the water to form a dispersion liquid. Under mechanical stirring, 1.5 kg of acetic acid was added dropwise. The acetic acid was added slowly, and then the reaction was carried out at 80°C for 1 hour. After the reaction was completed, water was added to adjust the concentration to 20%, and a transparent yttrium-zirconium composite sol solution IA was obtained.

[0045] (2) 1 kg of solution IA, 20 g of GPSTM (glycidyl ether oxypropyl trimethoxysilane), 10 g of C 12 H 26 S (dodecyl mercaptan), 10 g of Tween-60, 5 g of HX-3088 and 5 g of JFC were weighed and mixed to obtain solution IIA.

[0046] (3) The required weight of solution IA and solution IIA was weighed, water was added to adjust the concentration, and the mixture was uniformly mixed to obtain a self-emulsifying metal protection treatment liquid 1, which was used as a water-based anti-tarnish sealant for silver plating layer.

[0047] Example 2

[0048] (1) 3.08 kg of zirconium carbonate and 0.36 kg of yttrium carbonate were weighed and added to 10 kg of water to disperse the zirconium carbonate and yttrium carbonate in the water to form a dispersion liquid. Under mechanical stirring, 1.8 kg of acetic acid was added dropwise. The acetic acid was added slowly, and then the reaction was carried out at 60°C for 1 hour. After the reaction was completed, water was added to adjust the concentration to 10%, and a transparent yttrium-zirconium composite sol solution IB was obtained.

[0049] (2) Take 1 kg of solution IB, 20 g of GPSTE (glycidyloxypropyl triethoxysilane), 5 g of C 18 H 38 S (octadecyl mercaptan), 5 g of Tween-60, 5 g of HX-3088 and 5 g of JFC to obtain solution IIB;

[0050] (3) Take the required weight of solution IB and solution IIB, adjust the concentration with water, and mix uniformly. A self-emulsifying metal protection treatment solution 2 is obtained, which is used as a water-based anticorrosion sealant for silver plating.

[0051] Comparative Example 1

[0052] (1) Take 3.08 kg of zirconium carbonate and 0.36 kg of yttrium carbonate, add them to 10 kg of water to disperse the zirconium carbonate and yttrium carbonate in the water to form a dispersion liquid, and under mechanical stirring, add 1.8 kg of acetic acid dropwise. The acetic acid can be added slowly, and then react at 60°C for 1 hour. After the reaction is completed, add water to adjust the concentration to 10%, and a transparent yttrium-zirconium composite sol solution IB is obtained;

[0053] (2) Take 1 kg of solution IB, 5 g of C 18 H 38 S (octadecyl mercaptan), 5 g of Tween-60, 5 g of HX-3088 and 5 g of JFC to obtain solution C;

[0054] (3) Take the required weight of solution IB and solution C, adjust the concentration with water, and mix uniformly. A self-emulsifying metal protection treatment solution 3 is obtained.

[0055] Comparative Example 2

[0056] (1) Take 3.08 kg of zirconium carbonate and 0.036 kg of yttrium carbonate, add them to 5 kg of water to disperse the zirconium carbonate and yttrium carbonate in the water to form a dispersion liquid, and under mechanical stirring, add 1.5 kg of acetic acid dropwise. The acetic acid can be added slowly, and then react at 80°C for 1 hour. After the reaction is completed, add water to adjust the concentration to 20%, and a transparent yttrium-zirconium composite sol solution IA is obtained;

[0057] (2) Take 1 kg of solution IA, 20 g of GPSTM (glycidyloxypropyl trimethoxysilane), 10 g of Tween-60, 5 g of HX-3088 and 5 g of JFC to obtain solution D;

[0058] (3) Take the required weight of solution IA and solution D, adjust the concentration with water, and mix uniformly. A self-emulsifying metal protection treatment solution 4 is obtained.

[0059] Comparative Example 3

[0060] (1) Take 3.08 kg of zirconium basic carbonate and 0.036 kg of yttrium carbonate, add them to 5 kg of water to disperse the zirconium basic carbonate and yttrium carbonate in the water to form a dispersion liquid, under mechanical stirring, drop 1.5 kg of acetic acid, the acetic acid can be added slowly, then react at 80°C for 1 hour, after the reaction is completed, add water to adjust the concentration to 20%, to obtain a transparent yttrium-zirconium composite sol solution IA;

[0061] (2) Take 1 kg of solution IA, 10 g of Tween-60, 5 g of HX-3088 and 5 g of JFC to obtain solution E;

[0062] (3) Take the required weight of solution IA and solution E, add water to adjust the concentration, and mix uniformly. Obtain a self-emulsifying metal protection treatment liquid 5.

[0063] Comparative Example Four

[0064] Take 3.08 kg of zirconium basic carbonate and 0.36 kg of yttrium carbonate, add them to 10 kg of water to disperse the zirconium basic carbonate and yttrium carbonate in the water to form a dispersion liquid, under mechanical stirring, drop 1.8 kg of acetic acid, the acetic acid can be added slowly, then react at 60°C for 1 hour, after the reaction is completed, add water to adjust the concentration to 10%, to obtain a transparent yttrium-zirconium composite sol solution IB, as a metal protection treatment liquid 6.

[0065] Comparative Example Five

[0066] (1) Take 3.08 kg of zirconium basic carbonate and 0.36 kg of yttrium carbonate, add them to 10 kg of water to disperse the zirconium basic carbonate and yttrium carbonate in the water to form a dispersion liquid, under mechanical stirring, drop 1.8 kg of acetic acid, the acetic acid can be added slowly, then react at 60°C for 1 hour, after the reaction is completed, add water to adjust the concentration to 10%, to obtain a transparent yttrium-zirconium composite sol solution IB;

[0067] (2) Take 1 kg of solution IB, 20 g of GPSTE (glycidyl ether oxypropyl triethoxysilane), 5 g of C 16 H 38 S (hexadecyl mercaptan), 5 g of Tween-60, to obtain solution G;

[0068] (3) Take the required weight of solution IB and solution G, add water to adjust the concentration, and mix uniformly. Obtain a self-emulsifying metal protection treatment liquid 7, as a silver plating layer water-based anti-tarnish sealant.

[0069] Comparative Example Six

[0070] (1) Weigh 3.08 kg of zirconium basic carbonate, add it to 5 kg of water, disperse the zirconium basic carbonate in the water to form a dispersion liquid, under mechanical stirring, drop 1.5 kg of acetic acid, when dropping the acetic acid, it can also be slowly dropped, then react at 80°C for 1 hour, after the reaction is completed, add water to adjust the concentration to 20%, to obtain a transparent zirconium sol solution ID;

[0071] (2) Weigh 1 kg of solution ID, 20 g of GPTS (glycidyloxypropyltrimethoxysilane), 10 g of CTAB (cetyltrimethylammonium bromide), 10 g of S (dodecyl mercaptan), 10 g of Tween-60, 5 g of HX-3088 and 5 g of JFC, to obtain solution IIA; 12 H 26 S (dodecyl mercaptan), 10 g of Tween-60, 5 g of HX-3088 and 5 g of JFC, to obtain solution IIA;

[0072] (3) Weigh the required weight of solution ID and solution IIA, add water to adjust the concentration, mix uniformly, to obtain a self-emulsifying metal protection treatment solution 8.

[0073] In addition to the above examples and comparative examples, the following experiments are also carried out:

[0074] Weigh 3.08 kg of zirconium basic carbonate and 0.36 kg of yttrium carbonate, add them to 5 kg of water, disperse the zirconium basic carbonate and the yttrium carbonate in the water to form a dispersion liquid, under mechanical stirring, drop 0.6 kg of acetic acid, when dropping the acetic acid, it can also be slowly dropped, then react at 60°C for 2 hours, a transparent solution cannot be obtained. This also illustrates the importance of the reaction conditions of the present application.

[0075] The following Table 1 is a schematic table of the preparation methods of Example 1, Example 2, Comparative Example 1 to Comparative Example 6:

[0076] Table 1 Schematic table of the preparation methods of Example 1, Example 2, Comparative Example 1 to Comparative Example 6

[0077] Yttrium zirconium complex sol Silane coupling agent Alkyl mercaptan Emulsifiers, wetting agents, penetrants Treatment liquid 1 1 kg IA 20 g GPTS™ 10 g C 12 H 26 S]]> 10 g Tween-60, 5 g HX-3088, 5 g JFC Treatment liquid 2 1 kg IB 20 g GPTSETM 5g C 18 H 38 S]]> 5 g Tween-60, 5 g HX-3088, 5 g JFC Treatment liquid 3 1 kg IB 0 5g C 18 H 38 S]]> 5 g Tween-60, 5 g HX-3088, 5 g JFC Treatment liquid 4 1 kg IA 20 g GPTS™ 0 10 g Tween-60, 5 g HX-3088, 5 g JFC Treatment liquid 5 1 kg IA 0 0 10 g Tween-60, 5 g HX-3088, 5 g JFC Treatment liquid 6 1 kg IB 0 0 0 Treatment liquid 7 1 kg IB 20 g GPTSETM 5g C 16 H 34 S]]> 5 g Tween-60 Treatment liquid 8 1 kg ID 20 g GPTS™ 10 g C 12 H 26 S]]> 10 g Tween-60, 5 g HX-3088, 5 g JFC

[0078] It should be noted that in other embodiments of the present application, the yttrium-zirconium composite sol comprises Y2O3 and ZrO2; wherein the atomic ratio of Y and Zr is 1:10-1:100. The alkyl mercaptan can also be C 14 H 30 S (dodecyl mercaptan), C 15 H 30 S (dodecyl mercaptan), C 17 H 30 S (dodecyl mercaptan), C 13 H 30S (tridecyl mercaptan), the emulsifier can also be Tween-80, the wetting agent can be an alkyl phenol polyoxyethylene ether compound or a polyether modified dimethyl silicone compound, in addition to HX-3088, Ser-AD FN 211 or TEGOpren 5840 can also be used, the penetrant can use a fatty alcohol polyoxyethylene ether compound, in addition to JFC, JFC-2 or JFC-E can also be used.

[0079] The prepared treatment solution is mixed with water under stirring to obtain a dilute solution of the treatment solution, and a silver-plated part (coating thickness: 9 μm to 12 μm) cleaned is immersed in the dilute solution of the treatment solution for 5 min, and then the silver-plated part is rinsed and naturally dried. Then, relevant performance tests are carried out, wherein the discoloration experiment is immersed in 1% K2S aqueous solution for 1 h, and the acid salt spray test is carried out according to GB / T 10125-2012 artificial atmosphere corrosion test for 192 h.

[0080] The test results of the silver-plated part are shown in Table 2 below:

[0081] Table 2 Test results of silver-plated part

[0082] Serial number Treatment liquid [Results of K2S soaking] Acid salt spray test High-temperature baking acid salt spray test 1 2% treatment liquid 1 silver-white appearance no rust spots no rust spots 2 1% treatment liquid 1 silver-white appearance no rust spots no rust spots 3 3% treatment liquid 2 silver-white appearance no rust spots no rust spots 4 4% treatment liquid 2 silver-white appearance no rust spots no rust spots 5 2% treatment liquid 3 slight discoloration no rust spots no rust spots 6 2% treatment liquid 4 severe discoloration no rust spots no rust spots 7 2% treatment liquid 5 severe discoloration no rust spots no rust spots 8 2% treatment liquid 6 severe discoloration obvious rust spots obvious rust spots 9 2% treatment liquid 7 severe discoloration obvious rust spots obvious rust spots 10 2% treatment liquid 8 silver-white appearance no rust spots obvious rust spots

[0083] In the high-temperature baking acid salt spray test, the silver-plated part immersed in the treatment solution is baked at 900 DEG C for 1 h.

[0084] From the results in Table 2, it can be seen that:

[0085] (1) From the experimental results of serial number 5, serial number 6 and serial number 7, it can be seen that the addition of silane coupling agent and alkyl mercaptan can improve the K2S discoloration resistance of the water-based anti-discoloring sealing agent, and the silane coupling agent and the alkyl mercaptan are indispensable.

[0086] (2) From the experimental results of serial number 8, serial number 9 and serial number 10, it can be seen that the wetting agent and the penetrant can assist the penetration of the sol in the coating hole, improve the sealing effect, and the sealing effect is poor without adding.

[0087] (3) From the experimental results of serial number 10, it can be seen that the addition of yttrium can improve the high-temperature stability of the sealing agent, and the sol does not contain yttrium, and the acid salt spray resistance decreases after high-temperature baking.

[0088] (4) From the experimental results of serial number 1, serial number 2, serial number 3 and serial number 4, it can be seen that the sealing agent of the application has the dual functions of preventing silver discoloration and sealing silver coating holes, and has high high-temperature stability.

[0089] The application also provides a preparation method of the anti-discoloring film, and the specific steps include:

[0090] The silver plating water-based anti-tarnish sealing agent is diluted;

[0091] The surface silver plating part is immersed in the diluted sealing agent, or the diluted sealing agent is coated on the surface silver plating part, and an anti-tarnish film is formed on the surface of the silver plating.

[0092] In practical application, when the silver plating part is treated by the sealing agent, the sealing agent is diluted by water based on the total weight, and the solid content can be diluted to 1% to 5%. Then, the silver plating part is immersed in the diluted sealing agent or the diluted sealing agent is coated on the silver plating part. After a certain time, the silver plating part is taken out, washed and naturally dried.

[0093] The sealing agent can form an assembly film on the surface of the silver plating to slow down the tarnishing of the silver plating, and can effectively seal the pores of the silver plating. The silver plating treated by the anti-tarnish sealing agent has high high-temperature stability and can withstand 900℃ high-temperature baking.

[0094] The above is only a preferred embodiment of the present application and is not intended to limit the present application. The present application can be variously changed and modified for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A water-based anti-discoloration sealant for silver plating, characterized in that, Based on a total mass of 100%, the mass percentage of each component is as follows: Yttrium-zirconium composite sol: 10-20%; Silane coupling agent: 1%–5%; Alkyl thiols: 0.5%–2%; Emulsifier: 0.5%–2%; Wetting agent: 0.1%~1%; Penetrant: 0.1%–1%; Balance: Water; The yttrium-zirconium composite sol comprises Y₂O₃ and ZrO₂; wherein the atomic ratio of Y to Zr is 1:10 to 1:100; The emulsifier is Tween-60 or Tween-80; the wetting agent is an alkylphenol polyoxyethylene ether compound or a polyether-modified dimethylsiloxane compound; and the penetrant is a fatty alcohol polyoxyethylene ether compound.

2. The water-based anti-discoloration sealant for silver plating according to claim 1, characterized in that, The silane coupling agent is glycidyl etheroxypropyltrimethoxysilane or glycidyl etheroxypropyltriethoxysilane.

3. The water-based anti-discoloration sealant for silver plating according to claim 2, characterized in that, The alkyl thiol is an A-alkane thiol, wherein 12 ≤ A ≤ 18.

4. The water-based anti-discoloration sealant for silver plating according to claim 3, characterized in that, The alkyl thiol is dodecyl thiol, tetradecyl thiol, hexadecyl thiol, or octadecyl thiol.

5. A method for preparing an aqueous anti-discoloration sealant for a silver plating layer according to any one of claims 1 to 4, characterized in that, include: S1, basic zirconium carbonate and yttrium carbonate are dispersed in water, and acetic acid is added dropwise while stirring to carry out the reaction until the solution is clear, thus obtaining solution I; S2, mix the silane coupling agent, alkyl thiol, penetrant, wetting agent and emulsifier evenly to obtain solution II; S3, mix solution I and solution II, add water to adjust the concentration, and mix thoroughly to complete the preparation.

6. The method for preparing a water-based anti-discoloration sealant for silver plating according to claim 5, characterized in that, In step S1, the molar ratio of acetic acid and zirconium is 2:1 to 3:

1.

7. The method for preparing a water-based anti-discoloration sealant for silver plating according to claim 5 or 6, characterized in that, In step S1, the reaction is carried out at 70–80°C.

8. A method for preparing an anti-discoloration film, characterized in that, include: The silver plating layer according to any one of claims 1 to 4 is diluted with an aqueous anti-discoloration sealant; The component with a silver plating is immersed in a diluted sealant, or the diluted sealant is applied to the component with a silver plating to form an anti-discoloration film on the silver plating surface.