Sulfite electroforming gold liquid and preparation method thereof

Abstract

The invention discloses a sulfite gold electroforming solution and a preparation method thereof. The gold electroforming solution preferably comprises the following components: 10-16 g / L of sodium gold sulfite, 80-100 g / L of sodium sulfite, 40-55 g / L of sodium citrate, 10-15 g / L of disodium ethylene diamine tetraacetate, 50-70 g / L of disodium hydrogen phosphate, 1.5 g / L of sodium m-nitrobenzoate, 20-50 mg / L of antimony potassium tartrate and 10-50 mg / L of ammonium chloroplatinate. Hard gold ornaments manufactured by adopting the plating solution are high in purity and good in toughness, the hardness is easy to adjust, an electroforming gold layer contains trace precious metal platinum, the electroforming gold layer is more easily accepted by customers, and jewelry manufacturers can meet the requirements of various types of hard gold ornaments without opening more electroforming cylinders.

Description

Technical Field

[0001] The invention belongs to the technical field of gold plating, and in particular relates to a sulfite electroforming gold liquid and a preparation method thereof. Background Art

[0002] Gold has a long history of being used in jewelry. Since ancient times, the production process of gold jewelry has been mainly handmade. In recent years, with the continuous innovation and development of various metal processing technologies, the production process of gold jewelry has also made great progress. Hard gold electroforming technology is a novel gold jewelry production process that has emerged in recent years. This process is to make gold liquid and prepare it into an electroplating solution. After that, it is electrochemically formed on the surface of a low-temperature metal model or a paraffin model after conductive treatment. A layer of pure gold plating of more than 100 microns is formed, and then the low-temperature metal or paraffin inside the model is removed to form a pure gold jewelry with a hollow structure inside. The weight of hard gold electroforming jewelry of the same size is less than one-third of that of traditional crafts, but the hardness is more than 3 times higher, and it is not easy to deform or scratch during wearing. Especially for some complex and delicate pure gold jewelry, the hard gold electroforming process has great advantages.

[0003] At present, the hard gold electroforming solution on the market generally adopts the cyanide system. This type of gold electroforming system is easy to operate, has good stability, and is relatively low in cost, so it is widely used. However, cyanide is a highly toxic substance and has huge potential risks in storage, production, and wastewater treatment. Its application must be strictly controlled, which brings many inconveniences to hard gold electroforming manufacturers. In recent years, cyanide-free sulfite hard gold electroforming technicians have become popular in the jewelry industry. Using this type of plating solution for electroforming, the gold layer has a bright, flat, and delicate appearance, and its hardness is higher than that of cyanide electroforming gold. The entire production process avoids the use of highly toxic cyanide, so it is widely favored by manufacturers and the market. At present, this type of cyanide-free system has a tendency to completely replace the cyanide electroforming system.

[0004] In recent years, as the price of gold has repeatedly hit new highs, the production cost and sales price of gold jewelry have increased dramatically, forcing major jewelry manufacturers to tend to hard gold styles with fine shapes, small weights and thinner gold layers, reducing costs by reducing the amount of gold used. At present, some hard gold filigree jewelry with a gold layer thickness of less than 100 microns have appeared on the market. These jewelry have complex shapes, small weights, and thin gold layers, which require extremely high hardness and toughness of electroplated gold. The Vickers hardness of hard gold jewelry currently on the market made by the cyanide hard gold electroplating system is generally around 80HV. Although this type of hard gold jewelry has good toughness, the hardness of the gold layer is low and the supporting force is insufficient, and it is easy to deform during wearing. The hard gold jewelry made by the cyanide-free sulfite gold plating system on the market generally has a hardness of around 120HV. Although this type of hard gold jewelry has high supporting force, the thin gold layer is not tough enough, and it is easy to break under compression during wearing. Some manufacturers also increase the Vickers hardness of the gold layer to 130HV or even higher by adding base metal ions such as copper, cobalt, nickel, indium, and antimony to the sulfite gold plating system. However, the addition of base metal elements will not only lead to insufficient gold purity, but also make the gold layer more brittle and easy to break. Summary of the invention

[0005] In order to solve the problems raised in the above background technology, the present invention provides the following technical solutions: a sulfite electroforming gold liquid, which comprises: 5-20 g / L of gold sulfite salt (in terms of gold), 60-120 g / L of complexing agent, 40-80 g / L of stabilizer, 40-80 g / L of buffer, 1-2 g / L of wetting agent, 5-200 mg / L of brightener, and 0-80 mg / L of hardener.

[0006] A further solution is: the gold sulfite is one of ammonium gold sulfite, sodium gold sulfite or potassium gold sulfite, preferably sodium gold sulfite, and the dosage is preferably 10-16 g / L;

[0007] A further solution is: the complexing agent is one of ammonium sulfite, sodium sulfate or potassium sulfite, preferably sodium sulfite, and the dosage is preferably 80-100 g / L;

[0008] A further solution is: the stabilizer is one of ammonium citrate, sodium citrate or potassium citrate and ethylenediaminetetraacetate, preferably sodium citrate and disodium ethylenediaminetetraacetate, wherein sodium citrate is 40-55 g / L and disodium ethylenediaminetetraacetate is 10-15 g / L;

[0009] A further solution is: the buffer is one of diammonium hydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate, preferably disodium hydrogen phosphate, and the amount thereof is 50-70 g / L;

[0010] A further solution is: the wetting agent is sodium m-nitrobenzoate, preferably used in an amount of 1.5 g / L;

[0011] A further solution is: the brightener is one of sodium telluride, selenic acid, and potassium antimony tartrate, preferably potassium antimony tartrate, and the dosage is 20-50 mg / L;

[0012] Further solution: the hardener is one of ammonium chloroplatinate, sodium chloroplatinate or potassium chloroplatinate, preferably ammonium chloroplatinate, and the dosage is 10-50 mg / L.

[0013] In a further embodiment, the composition of the sulfite electroforming gold solution is preferably: 10-16 g / L of sodium gold sulfite, 80-100 g / L of sodium sulfite, 40-55 g / L of sodium citrate, 10-15 g / L of disodium ethylenediaminetetraacetic acid, 50-70 g / L of disodium hydrogen phosphate, 1.5 g / L of sodium m-nitrobenzoate, 20-50 mg / L of potassium antimony tartrate, and 10-50 mg / L of ammonium chloroplatinate.

[0014] In a further embodiment, the working conditions of the sulfite electroforming gold liquid are:

[0015] pH: Ph7.2-7.8;

[0016] Temperature: 35-65℃;

[0017] Current density: 0.5-2 amperes / square decimeter.

[0018] In a further embodiment, the preferred working conditions of the sulfite electroforming gold liquid are:

[0019] pH: pH7.3-7.6

[0020] Temperature: 40-60℃

[0021] Current density: 0.75-1.5 amperes / square decimeter

[0022] On the other hand, a sulfite electroforming gold liquid, the preparation method of which comprises the following steps:

[0023] Preparation of S10 platinum salt: 2.28 g of commercially available ammonium chloroplatinate, 2 g of sodium citrate and 2 g of disodium hydrogen phosphate were placed in a beaker, pure water was added, and the mixture was heated and boiled until all the solid powder was dissolved;

[0024] Preparation of S20 antimony salt: Take 1 gram of potassium antimony tartrate and place it in a beaker, add pure water, and stir until it is completely dissolved.

[0025] Preparation of S30 sulfite electroplating gold solution:

[0026] Add pure water to the S301 glass beaker and heat to 60℃-80℃;

[0027] S302 weighs the measured sodium sulfite, disodium hydrogen phosphate, sodium citrate, disodium ethylenediaminetetraacetate and sodium m-nitrobenzoate and adds them into the glass container S301 in sequence, stirring until all are dissolved;

[0028] S303 weighs a measured amount of commercially available sodium gold sulfite solution, adds it to the S302 solution, and stirs evenly;

[0029] S304 weighs the measured amount of S10 platinum salt and S20 antimony salt, adds them to the S303 solution and stirs evenly;

[0030] S305 Use 30% phosphoric acid or sodium hydroxide solution to adjust the pH value of S304 plating solution to the required range and then try plating.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a cyanide-free sulfite electroplating gold liquid and a preparation method. The hard gold jewelry made by using the plating solution has high purity and good toughness, is not easily deformed or broken by extrusion, and can achieve a wide range of adjustable hardness from low to high hardness of the electroplated gold layer by controlling the amount of platinum salt added as a hardener. Jewelry manufacturers do not need to open more electroplating cylinders to meet the requirements of various types of hard gold jewelry. Secondly, while adding platinum salts to the electroplating gold liquid provided by the present invention, brightener antimony salts are also indispensable. Trace amounts of platinum and antimony elements will be present in the hard gold layer at the same time. Surprisingly, the addition of platinum ions will reduce the antimony content while increasing the hardness and toughness of the electroplated gold layer, making the gold purity of the hard gold jewelry higher. In addition, the electroplated gold layer contains trace amounts of precious metal platinum, which is more easily accepted by customers than the hard gold layer containing base metal elements such as copper, cobalt, nickel, and indium in the current market. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] The present invention discloses that the raw materials used in the following embodiments are all commercially available unless otherwise specified. Antimony salt, a brightener, and platinum salt, a hardener, are required in the embodiments, and the two additives are obtained according to the following steps:

[0035] Preparation of platinum salt: 2.28 g of commercially available ammonium chloroplatinate, 2 g of sodium citrate and 2 g of disodium hydrogen phosphate were placed in a 1-liter beaker, 100 ml of pure water were added, and the mixture was heated and boiled in a resistance furnace until all the solid powder was dissolved, and then diluted to 1000 g for later use. The platinum ion content was 1 mg / g of solution.

[0036] Preparation of antimony salt: Take 1 gram of potassium antimony tartrate and place it in a 1-liter beaker, add 100 ml of pure water, stir until it is completely dissolved and dilute to 1000 grams for use. The content of potassium antimony tartrate is 1 mg / g.

[0037] In the embodiment, a unified jewelry model is selected, and the preliminary preparation and the later demoulding process are performed according to the following steps:

[0038] The cylindrical low-temperature alloy model is fixed on the electroplating hanger, first electroplated in an alkaline copper electroplating tank for 5 minutes, then electroplated in an acid copper electroplating tank for 5 minutes after cleaning, and then electroplated in an acid nickel electroplating tank for 5 minutes, and then the model is removed and used in various embodiments. The jewelry model after electroplating gold is shaken in a 200°C oven to remove the molten low-temperature alloy for two hours until it is completely removed, then boiled in a 30% nitric acid solution for 1 hour to remove the copper and nickel layers, and finally dried in a 200°C oven for 1 hour to test various properties.

[0039] Embodiment 1:

[0040] Add about 600 ml of pure water to a 1-liter beaker, heat to 70°C, add 85 g of sodium sulfite, 60 g of disodium hydrogen phosphate, 50 g of sodium citrate, 10 g of disodium ethylenediaminetetraacetic acid, 1.5 g of sodium m-nitrobenzoate, stir until all are dissolved, add 16 g of gold sodium sulfite solution, add 20 mg of potassium antimony tartrate solution, adjust the Ph value of the plating solution to 7.5, add the plating solution to 1 liter and then test plating. The working conditions are as follows:

[0041] pH: 7.5

[0042] Bath temperature: 55°C

[0043] Current density: 0.5A / dm2

[0044] Plating solution circulation: electromagnetic stirring

[0045] Electroforming time: 10 hours

[0046] According to the above conditions, after 10 hours of electroforming, a hard gold ornament with a uniform, smooth and bright gold layer was obtained.

[0047] Embodiment 2:

[0048] The same formula as in Example 1 was used, except that the amount of platinum salt added was 15 mg / L of plating solution. Electroforming was performed under the working conditions of Example 1, and after 10 hours, a hard gold ornament with a uniform, smooth and bright gold layer was obtained.

[0049] Embodiment three:

[0050] Add about 600 ml of pure water to a 1-liter beaker, heat to 80°C, add 90 g of sodium sulfite, 60 g of disodium hydrogen phosphate, 50 g of sodium citrate, 12 g of disodium ethylenediaminetetraacetic acid, 1.5 g of sodium m-nitrobenzoate, stir until all are dissolved, add 16 g of gold sodium sulfite solution, 40 mg of potassium antimony tartrate solution, 30 mg of platinum salt solution, adjust the Ph of the plating solution to 7.5, and add the plating solution to 1 liter before trial plating. The working conditions are as follows:

[0051] pH: 7.5

[0052] Bath temperature: 55°C

[0053] Current density: 0.5A / dm2

[0054] Plating solution circulation: electromagnetic stirring

[0055] Electroforming time: 10 hours

[0056] According to the above conditions, after 10 hours of electroforming, a hard gold ornament with a uniform, smooth and bright gold layer was obtained.

[0057] Embodiment 4:

[0058] The same formula as in Example 3 was used, except that the amount of platinum salt added was 50 mg / L of plating solution. Electroforming was performed according to the conditions in Example 3, and after 10 hours, a hard gold ornament with a uniform, smooth and bright gold layer was obtained.

[0059] The test data of the samples in each embodiment are shown in Table 1. It should be noted that the "electroformed gold hardness" in the table refers to the hardness directly measured after the jewelry is electroformed with gold, and the "finished product hardness" refers to the hardness measurement of the finished product after the jewelry is electroformed with gold and subjected to processes such as demolding, acid boiling and drying.

[0060] Table 1 Comparison of gold layer hardness and content of each component

[0061]

[0062]

[0063] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0064] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sulfite electroforming gold liquid, characterized in that: The invention comprises the following ingredients: 5-20 g / L of gold sulfite, 60-120 g / L of complexing agent, 40-80 g / L of stabilizer, 40-80 g / L of buffer, 1-2 g / L of wetting agent, 5-200 mg / L of brightener and 0-80 mg / L of hardening agent.

2. The sulfite electroforming gold liquid according to claim 1, characterized in that: The gold sodium sulfite is 10-16 g / L, sodium sulfite is 80-100 g / L, sodium citrate is 40-55 g / L, disodium ethylenediaminetetraacetate is 10-15 g / L, disodium hydrogen phosphate is 50-70 g / L, sodium m-nitrobenzoate is 1.5 g / L, potassium antimony tartrate is 20-50 mg / L, and ammonium chloroplatinate is 10-50 mg / L.

3. The sulfite electroforming gold liquid according to claim 1, characterized in that: Its further working conditions are: pH7.3-7.6; Temperature 40-60℃; The current density is 0.75-1.5 amperes per square decimeter.

4. A method for preparing sulfite electroforming gold liquid, characterized in that: The following steps are included: Preparation of S10 platinum salt: 2.28 g of commercially available ammonium chloroplatinate, 2 g of sodium citrate and 2 g of disodium hydrogen phosphate were placed in a beaker, pure water was added, and the mixture was heated and boiled until all the solid powder was dissolved; Preparation of S20 antimony salt: Take 1 gram of potassium antimony tartrate and place it in a beaker, add pure water, and stir until it is completely dissolved; Preparation of S30 sulfite electroforming gold solution; Add pure water to the S301 glass beaker and heat to 60℃-80℃; S302 weighs the measured sodium sulfite, disodium hydrogen phosphate, sodium citrate, disodium ethylenediaminetetraacetate and sodium m-nitrobenzoate and adds them into the glass container S301 in sequence, stirring until all are dissolved; S303 weighs a measured amount of commercially available sodium gold sulfite solution, adds it to the S302 solution, and stirs evenly; S304 weighs the measured amount of S10 platinum salt and S20 antimony salt, adds them to the S303 solution and stirs evenly; S305 Use 30% phosphoric acid or sodium hydroxide solution to adjust the pH value of S304 plating solution to the required range and then try plating.

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