A precious metal electroplating method for changing the color of metal surface

Abstract

The invention discloses a precious metal electroplating method for changing the color of a metal surface, comprising the following steps: preparing the precious metal into metal wires, weaving the metal wires to obtain a first braid; pre-treating the braid obtained in the step to obtain a second braid; electroplating the second braid obtained in the step to obtain the precious metal with the changed metal surface color; the pre-treatment is sequentially treated with solution A, acid, and water, wherein the solution A comprises sodium hydroxide, sodium silicate, a surfactant, and water; the electroplating solution used in the electroplating comprises a color plating compound, potassium citrate, potassium carbonate, sodium hydroxide, and water. The electroplating process of the invention and different color plating compounds enable the precious metal braid to be electroplated into different colors, and the process is simple and the service life is long.

Description

Technical Field

[0001] The present invention relates to the field of electroplating technology, and more particularly to a noble metal electroplating method for changing the color of a metal surface, and further to a noble metal electroplating method for changing the color of a metal surface by non-adhesive surface treatment. Background Art

[0002] Electroplating is the process of plating a thin layer of metal or alloy on the metal surface using the principle of electrolysis to prevent metal oxidation, improve wear resistance, conductivity, reflectivity, corrosion resistance and enhance aesthetics. The colors of jewelry made of precious metals include natural color and paint color. The natural color is the color of the precious metal itself, and the paint color is painted on the outside of the precious metal jewelry. The color of the paint is adjusted according to demand. Since the paint color is sprayed on the surface of the precious metal by a spray paint equipment, the purpose of protecting the precious metal body is achieved. However, the paint on the surface of the precious metal has a short life and is easy to fall off, which affects the use of the precious metal jewelry.

[0003] Chinese patent application CN201710740348.8 discloses a thermochromic process for precious metals, including the following steps: a. Apply a black primer on the surface of the precious metal first, and then dry it; b. Wait for the surface temperature of the precious metal to drop below room temperature, and then apply the thermochromic paint to the primer on the surface of the precious metal to form a thermochromic coating, and dry it; c. After drying, apply a protective layer on the surface of the thermochromic coating, and obtain the finished product after drying. The thermochromic process provided by the invention is simple to operate, environmentally friendly and healthy, and the precious metal products obtained are colorful and diverse, which improves the ornamental value of the precious metal products. Changing the color by coating has a short lifespan and is easy to fall off.

[0004] Chinese patent application CN202110887358.0 discloses a coating method for precious metal postcards, which includes the following steps: selecting a precious metal plate of suitable thickness, cutting and polishing the precious metal plate according to the design size of the postcard, and then placing the cut plate into an ultrasonic cleaning device for cleaning. The cleaning water uses hot water above 70°C, and one or more of salt, strong tea, silver washing water, vinegar, alcohol, and ammonia water are added to the hot water. A protective film can be formed on the surface of the postcard using a coating solvent, an inert mixed gas, and a coating power supply. The protective film is used to protect the postcard to prevent water vapor and oxygen in the air from reacting with the surface of the precious metal, and after a period of playing, there will be no discoloration, so the postcard can be protected. Before coating, it also includes applying epoxy phenolic paint, UV primer, and then drying and curing. On the one hand, the steps are more cumbersome, and on the other hand, the stability of the coating directly affects the life of the protective film.

[0005] Therefore, there is currently a lack of a simple, effective, and long-life precious metal electroplating method that does not require surface treatment and simultaneously changes the color of the metal surface to meet the diverse needs of precious metal jewelry. Summary of the invention

[0006] In view of this, and in view of the deficiencies in the prior art, an object of the present invention is to provide a precious metal electroplating method for changing the color of a metal surface. The precious metal electroplating method of the present invention has no attachments, has a long service life, and can electroplate different colors according to different needs.

[0007] To solve the above technical problems, the present invention is implemented by the following scheme: A precious metal electroplating method for changing the color of a metal surface of the present invention comprises the following steps:

[0008] (1) preparing a precious metal into metal wires, and weaving the metal wires to obtain a first braided fabric;

[0009] (2) pre-treating the first woven fabric obtained in step (1) to obtain a second woven fabric;

[0010] (3) electroplating the second braid obtained in step (2) to obtain a precious metal that changes the color of the metal surface;

[0011] The pretreatment is sequentially immersing in solution A, acid, and water, wherein the solution A comprises sodium hydroxide, sodium silicate, a surfactant, and water;

[0012] In step (3), the electroplating solution used in the electroplating comprises a plating compound, potassium citrate, potassium carbonate, sodium hydroxide and water.

[0013] Furthermore, in step (1), the diameter of the metal wire is 0.01-0.15 mm, and more preferably 0.01-0.1 mm.

[0014] Preferably, in step (1), the step of preparing the metal wire comprises: vacuum melting, directional continuous casting and wire drawing.

[0015] Further preferably, in step (1), the step of preparing the metal wire comprises: vacuum melting and directionally continuous casting the precious metal at 900-1400°C for 1-5h to form a metal rod with a diameter of 30-40mm; subjecting the metal rod to a multiple-pass rough drawing process to obtain a coarse metal wire with a diameter of 0.18-5mm; and subjecting the coarse metal wire to a multiple-pass fine drawing process to obtain a metal wire with a diameter of 0.01-0.15mm.

[0016] It is further preferred that: the precious metal is vacuum melted and directionally continuously cast at 1000-1200°C for 1-3h to form a metal rod with a diameter of 35mm; the metal rod is subjected to a multi-pass rough drawing process to obtain a coarse metal wire with a diameter of 0.2-2mm; the coarse metal wire is subjected to a multi-pass fine drawing process to obtain a metal wire with a diameter of 0.01-0.1mm.

[0017] Preferably, the metal wire further includes a heat treatment step before weaving. Further preferably, the heat treatment is performed at 250-350° C. and the heat treatment speed is 1-3 m / s.

[0018] Furthermore, in step (2), according to mass percentage, the solution A comprises 10-50% sodium hydroxide, 10-20% sodium silicate, 1-10% surfactant and the balance water. Furthermore, the solution A comprises 30% sodium hydroxide, 12% sodium silicate, 5% surfactant and the balance water.

[0019] Furthermore, the surfactant is a combination of zeinol, lauryl alcohol and sodium dodecyl mercaptan.

[0020] Furthermore, the mass ratio of corn alcohol, lauryl alcohol and sodium dodecyl mercaptan is 8-12:0.1-1.5:1-5, and further 10:1:3.

[0021] Furthermore, in step (2), the acid is sulfuric acid, more preferably sulfuric acid with a volume concentration of 45-55%, most preferably sulfuric acid with a volume concentration of 50%.

[0022] Furthermore, in step (2), the water is pure water.

[0023] Furthermore, step (3) is specifically as follows: the second braided fabric obtained in step (2) is placed on a plating rack and sent into a plating tank, wherein the plating tank is filled with a plating solution for electroplating.

[0024] Furthermore, the electroplating solution comprises, by mass fraction, 5%-16% of a color plating compound, 2%-10% of potassium citrate, 3%-12% of potassium carbonate, 5%-15% of sodium hydroxide, and the balance of water. Furthermore, the electroplating solution comprises, by mass fraction, 10% of a color plating compound, 5% of potassium citrate, 5% of potassium carbonate, 10% of sodium hydroxide, and the balance of water.

[0025] Furthermore, the color plating compound includes at least one of gold compounds, nickel compounds, palladium nickel compounds, palladium compounds, copper compounds, zinc compounds, tin compounds, silver compounds, and chromium compounds. Since nickel compounds, palladium compounds, copper compounds, zinc compounds, tin compounds, silver compounds, and chromium compounds undergo a substitution reaction with precious metals during electroplating, different colors are attached to the surface of the precious metals.

[0026] Furthermore, the electroplating conditions are: a DC power supply, the current density of the DC power supply output is 1.5-2.0A / dm 2 , temperature is 50-65℃, and electroplating time is 60s-120s.

[0027] Furthermore, the electroplating conditions are: temperature of 55° C. and electroplating time of 95 s.

[0028] Furthermore, after the electroplating is completed, the method further comprises step (4): vacuum suspending the electroplated second braided fabric and sending it to a steam cleaning device for cleaning and drying.

[0029] Furthermore, the temperature in the steam cleaning equipment is 110°C-150°C.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] (1) The precious metal electroplating method of the present invention does not use a baking varnish process. Instead, the precious metal braid is electroplated into different colors through the electroplating process and the substitution reaction between different color-plating compounds and precious metals. This makes the precious metal jewelry have rich and colorful colors, and the precious metal jewelry is diversified to meet different jewelry needs.

[0032] (2) The precious metal electroplating method of the present invention is simple, convenient and efficient.

[0033] (3) The color-changing precious metal obtained by the precious metal electroplating method of the present invention has stable color, long service life, and is not easy to fall off. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The picture of the ornaments prepared by the present invention, wherein the ropes of each color are a bundle subjected to color plating treatment. DETAILED DESCRIPTION

[0035] The following non-limiting examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary description of the scope of the present invention, and those skilled in the art can make various changes and modifications to the invention of the present invention based on the disclosed content, and they should also fall within the scope of the present application.

[0036] The present invention is further described below by way of specific examples. The various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all weight contents. Unless otherwise specified, it is understood that the process is carried out at room temperature.

[0037] In the embodiment of the present invention, the weaving can be a conventional weaving method in the art, the purpose of which is to prepare the drawn metal wire into a rope bundle with a diameter of 2.5±0.2 mm again. As a specific embodiment, the weaving methods used in the following embodiments are: the weaving method is: weaving with a continuous S-bend structure in the weft direction to form an inverted U-shaped peak point and a U-shaped valley point; in the two adjacent single ropes in the weft direction, the rope bodies on both sides of the inverted U-shaped peak point of the next row of single ropes are inserted between the two adjacent U-shaped valley points of the previous row of single ropes, and all the single ropes on the weft are woven on the warp to form a closed-loop mesh body.

[0038] Example 1

[0039] (1) Solution A is prepared: comprising, by mass fraction, 30% sodium hydroxide, 12% sodium silicate, 5% surfactant and the balance water.

[0040] Thoroughly mix corn alcohol, lauryl alcohol, and sodium dodecyl mercaptan in a mass ratio of 10:1:3 to obtain a surfactant for use; add a formula amount of sodium hydroxide to pure water, stir to dissolve, add a formula amount of surfactant while stirring, add a formula amount of sodium silicate, stir thoroughly to obtain solution A.

[0041] (2) Preparation of electroplating solution: comprising, by mass fraction, 10% zinc oxide, 5% potassium citrate, 5% potassium carbonate, 10% sodium hydroxide and the balance water.

[0042] Add the formulated amounts of zinc oxide, potassium citrate, potassium carbonate and 1% sodium hydroxide to pure water in sequence, stir thoroughly to dissolve, and obtain an electroplating solution.

[0043] (3) vacuum melting and directional continuous casting of precious metal (gold 18k gold) at 1050° C. for 2 h to form a metal rod with a diameter of 35±2 mm; the metal rod is subjected to a multi-pass rough drawing process to obtain a coarse metal wire with a diameter of 0.8-1.2 mm; the coarse metal wire is subjected to a multi-pass fine drawing process to obtain a metal wire with a diameter of 0.02-0.06 mm, and heat treatment is performed at 320° C. at a heat treatment speed of 1-3 m / s, and the heat-treated metal wires are braided to obtain a first braid;

[0044] (4) The first braided fabric obtained in step (1) is sequentially immersed in solution A (45 min), 50% by volume sulfuric acid (10 min), and pure water (10 min) to obtain a second braided fabric;

[0045] (5) The second braided fabric obtained in step (2) is placed on a plating rack and sent into a plating tank, wherein the plating tank is filled with the prepared plating solution for electroplating. The electroplating conditions are: a DC power supply is used, and the current density output by the DC power supply is 1.8 A / dm 2 , temperature is 55℃, and plating time is 95s;

[0046] (6) The second braided fabric after electroplating is placed in a vacuum suspension, sent to a steam cleaning device for cleaning at 135° C., and dried to obtain a precious metal with a changed metal surface color.

[0047] Example 2

[0048] Solution A: comprises 50% sodium hydroxide, 20% sodium silicate, 1% surfactant and the balance water according to mass fraction.

[0049] Electroplating solution: comprises, by mass fraction, 5% zinc oxide, 2% potassium citrate, 3% potassium carbonate, 5% sodium hydroxide and the balance water.

[0050] The remaining steps are the same as in Example 1.

[0051] Example 3

[0052] Solution A: includes 10% sodium hydroxide, 10% sodium silicate, 10% surfactant and the balance water according to mass fraction.

[0053] Electroplating solution: comprises, by mass fraction, 16% zinc oxide, 10% potassium citrate, 12% potassium carbonate, 15% sodium hydroxide and the balance water.

[0054] The remaining steps are the same as in Example 1.

[0055] Example 4

[0056] Corn alcohol, lauryl alcohol and sodium dodecyl mercaptan are fully mixed in a mass ratio of 8:0.1:1 to obtain a surfactant.

[0057] The remaining steps are the same as in Example 1.

[0058] Example 5

[0059] The thick metal wire is produced through multiple-pass fine drawing processes to obtain a metal wire with a diameter of 0.06-0.15 mm.

[0060] The remaining steps are the same as in Example 1.

[0061] Comparative Example 1

[0062] (1) Solution A is prepared: comprising, by mass fraction, 30% sodium hydroxide, 12% sodium silicate, 5% surfactant and the balance water.

[0063] Thoroughly mix corn alcohol, lauryl alcohol, and sodium dodecyl mercaptan in a mass ratio of 10:1:3 to obtain a surfactant for use; add a formula amount of sodium hydroxide to pure water, stir to dissolve, add a formula amount of surfactant while stirring, add a formula amount of sodium silicate, stir thoroughly to obtain solution A.

[0064] (2) Preparation of electroplating solution: comprising, by mass fraction, 10% zinc oxide, 5% potassium citrate, 5% potassium carbonate, 10% sodium hydroxide and the balance water.

[0065] Add the formulated amounts of zinc oxide, potassium citrate, potassium carbonate and 1% sodium hydroxide to pure water in sequence, stir thoroughly to dissolve, and obtain an electroplating solution.

[0066] (3) vacuum melting and directionally continuous casting of the precious metal at 1050°C for 2 h to form a metal rod with a diameter of 35±2 mm;

[0067] (4) The metal rod obtained in step (1) was sequentially immersed in solution A (45 min), 50% by volume sulfuric acid (10 min), and pure water (10 min);

[0068] (5) The metal rod treated by immersion in step (2) is placed on a plating rack and sent into a plating tank, which is filled with the prepared plating solution for electroplating. The electroplating conditions are: a DC power supply, the current density of the DC power supply output is 1.8A / dm 2 , temperature is 55℃, and plating time is 95s;

[0069] (6) The electroplated metal rod is placed in a vacuum suspension and sent to a steam cleaning device for cleaning and drying at 135° C. to obtain a precious metal with a changed metal surface color.

[0070] Comparative Example 2

[0071] Solution A: comprises 50% sodium hydroxide, 20% sodium silicate and the balance water according to mass fraction.

[0072] The remaining steps are the same as in Example 1.

[0073] Comparative Example 3

[0074] The surfactant is prepared by mixing corn alcohol and lauryl alcohol in a ratio of 10:1.

[0075] The remaining steps are the same as in Example 1.

[0076] Comparative Example 4

[0077] The surfactant is prepared by fully mixing corn alcohol, lauryl alcohol and sodium dodecyl mercaptan in a mass ratio of 1:1:1.

[0078] The remaining steps are the same as in Example 1.

[0079] Comparative Example 5

[0080] Electroplating solution: It includes 16% zinc oxide, 22% potassium carbonate, 15% sodium hydroxide and the balance water in terms of mass fraction.

[0081] The remaining steps are the same as in Example 1.

[0082] Comparative Example 6

[0083] (1) Solution A is prepared: comprising, by mass fraction, 30% sodium hydroxide, 12% sodium silicate, 5% surfactant and the balance water.

[0084] Thoroughly mix corn alcohol, lauryl alcohol, and sodium dodecyl mercaptan in a mass ratio of 10:1:3 to obtain a surfactant for use; add a formula amount of sodium hydroxide to pure water, stir to dissolve, add a formula amount of surfactant while stirring, add a formula amount of sodium silicate, stir thoroughly to obtain solution A.

[0085] (2) Preparation of electroplating solution: comprising, by mass fraction, 10% zinc oxide, 5% potassium citrate, 5% potassium carbonate, 10% sodium hydroxide and the balance water.

[0086] Add the formulated amounts of zinc oxide, potassium citrate, potassium carbonate and 1% sodium hydroxide to pure water in sequence, stir thoroughly to dissolve, and obtain an electroplating solution.

[0087] (3) vacuum melting and directional continuous casting of the precious metal at 1050° C. for 2 h to form a metal rod with a diameter of 35±2 mm; subjecting the metal rod to a multiple-pass rough drawing process to obtain a coarse metal wire with a diameter of 0.8-1.2 mm; subjecting the coarse metal wire to a multiple-pass fine drawing process to obtain a metal wire with a diameter of 0.18-0.22 mm, heat treating the metal wire at 320° C. at a heat treatment speed of 1-3 m / s, and braiding the heat-treated metal wire to obtain a first braid;

[0088] (4) The first braided fabric obtained in step (1) is sequentially immersed in solution A (45 min), 50% by volume sulfuric acid (10 min), and pure water (10 min) to obtain a second braided fabric;

[0089] (5) The second braided fabric obtained in step (2) is placed on a plating rack and sent into a plating tank, wherein the plating tank is filled with the prepared plating solution for electroplating. The electroplating conditions are: a DC power supply is used, and the current density output by the DC power supply is 1.8 A / dm 2 , temperature is 55℃, and plating time is 95s;

[0090] (6) The second braided fabric after electroplating is placed in a vacuum suspension, sent to a steam cleaning device for cleaning at 135° C., and dried to obtain a precious metal with a changed metal surface color.

[0091] Results test:

[0092] 20 samples of the products prepared in Examples 1-5 and Comparative Examples 1-6 were taken for the following tests:

[0093] (1) Accelerated stability test: Place the sample in an environment with a temperature of 40±1°C and a humidity of 90±2% for 6 months, and observe the surface changes after 1, 3, and 6 months;

[0094] (2) Thermal shock test: The test is conducted after being placed in an environment with room temperature and humidity of 60±2% for 3 months. One cycle is repeated alternately at -1°C for 30 min, 30°C for 2 min, and 70°C for 30 min. The test is stopped when abnormalities occur on the surface, and the average number of complete cycles is recorded.

[0095] (3) 3% potassium sulfide solution immersion test: The sample is completely immersed in a 3% potassium sulfide solution at room temperature, and the average time for the color change area to be less than 1% is calculated;

[0096] (4) Artificial sweat test: The test was conducted at room temperature. The sample was completely immersed in artificial sweat (5% sodium chloride + 10% lactic acid + 85% distilled water) for 24 h and 48 h, and the surface changes were observed.

[0097] (5) Conduct neutral salt spray resistance time test in a salt spray test chamber.

[0098] The results of the accelerated stability test are as follows:

[0099] Group January March June Example 1 No change No change No change Example 2 No change No change No change Example 3 No change No change No change Example 4 No change No change 9 pieces of color changing Example 5 No change No change No change Comparative Example 1 Uniform color change Uniform color change Uniform color change Comparative Example 2 Uniform color change Uniform color change Uniform color change Comparative Example 3 No change 15 pieces of color change Uniform color change Comparative Example 4 No change No change Uniform color change Comparative Example 5 No change 17 pieces of color change Uniform color change Comparative Example 6 No change No change Uniform color change

[0100] The rest of the test results are as follows:

[0101]

[0102]

[0103] The results show that the products prepared by the embodiments of the present invention have significantly extended service life and better coloring stability. The results of comparative example 1 show that the coloring stability can be improved by weaving the metal wire after drawing and then electroplating. Comparative examples 2-4 show that surfactants play an important role in the pretreatment of precious metals. Selecting suitable surfactants and adding them during pretreatment can improve the plating stability. Comparative example 5 shows that a suitable electroplating solution is more conducive to coloring stability. In addition, the applicant also found that in order to maintain a good coloring effect, it is very important to keep the diameter of the metal wire below 0.15 mm. When the diameter of the metal wire is too high, the stability will also be reduced.

[0104] According to the process of Example 1, different color plating compounds are replaced to obtain rope bundles of different colors, and to prepare ornaments with various colors, such as Figure 1 , overcoming the defect of single color of original precious metals.

[0105] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A precious metal electroplating method for changing the color of a metal surface, characterized in that: The following steps are involved: (1) Preparing a precious metal into a metal wire, and weaving the metal wire to obtain a first braid; the diameter of the metal wire is 0.01-0.15 mm; (2) pre-treating the first woven fabric obtained in step (1) to obtain a second woven fabric; (3) electroplating the second braid obtained in step (2) to obtain a precious metal that changes the color of the metal surface; The pretreatment is sequentially treated by immersion in solution A, acid and water, wherein the solution A comprises 10-50% sodium hydroxide, 10-20% sodium silicate, 1-10% surfactant and the balance water; wherein the surfactant is a combination of corn alcohol, lauryl alcohol and sodium dodecyl mercaptan, and the mass ratio of corn alcohol, lauryl alcohol and sodium dodecyl mercaptan is 8-12:0.1-1.5:1-5; In step (3), the electroplating solution used in the electroplating comprises, by mass fraction, 5%-16% of a plating compound, 2%-10% of potassium citrate, 3%-12% of potassium carbonate, 5%-15% of sodium hydroxide and the remainder of water.

2. The noble metal electroplating method for changing the color of a metal surface according to claim 1, characterized in that: In step (1), the diameter of the metal wire is 0.01-0.1 mm.

3. The precious metal electroplating method for changing the color of a metal surface according to claim 1, characterized in that: In step (1), the steps of preparing the metal wire include: vacuum melting, directional continuous casting and wire drawing.

4. The noble metal electroplating method for changing the color of a metal surface according to claim 3, characterized in that: In step (1), the step of preparing the metal wire includes: vacuum melting and directionally continuous casting the precious metal at 900-1400°C for 1-5h to form a metal rod with a diameter of 30-40mm; subjecting the metal rod to a multiple-pass rough drawing process to obtain a coarse metal wire with a diameter of 0.18-5mm; and subjecting the coarse metal wire to a multiple-pass fine drawing process to obtain a metal wire with a diameter of 0.01-0.15mm.

5. The noble metal electroplating method for changing the color of a metal surface according to claim 1, characterized in that: The metal wire also includes a heat treatment step before weaving, wherein the heat treatment is performed at 250-350° C. and the heat treatment speed is 1-3 m / s.

6. The noble metal electroplating method for changing the color of a metal surface according to claim 1, characterized in that: The electroplating conditions are: a DC power supply with a current density of 1.5-2.0 A / dm 2 , temperature is 50-65℃, and electroplating time is 60s-120s.

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