Electrolytic release formula and process for electroplating hanger

Abstract

The invention discloses an electroplating hanger electrolysis stripping formula and process, and relates to the technical field of stripping and stripping processes. The electroplating hanger electrolytic dehanging formula comprises the following components in parts by weight: 30-50 parts of sodium nitrate, 15-35 parts of ammonium nitrate, 15-30 parts of ammonium chloride, 15-25 parts of tartaric acid and 10-20 parts of citric acid. According to the electrolytic deplating formula of the electroplating hanger, rapid deplating of the surface of the hanger can be achieved at low cost, and a base material is not damaged.

Description

Technical Field

[0001] The present invention relates to the field of stripping and stripping processes, and particularly to an electrolytic stripping formula and process for electroplating fixtures. Background Art

[0002] The stripping of the coating on the fixture is an important process step. If the fixture is not stripped of the coating and directly used to hang the electroplated products with the coating, it will have a direct negative impact on the quality of the electroplated products. In the field of electroplating processing, the traditional stripping process for electroplating fixtures faces the problem of being difficult to balance efficiency and substrate protection. Traditional chemical stripping methods, such as concentrated nitric acid oxidation method, anti-dyeing salt method, etc., have a long stripping time. Especially for fixtures with complex shapes, the stripping is not complete, and the electrolytic stripping method is likely to cause serious corrosion of the fixtures.

[0003] Therefore, there is currently a lack of a method with low cost, capable of rapid stripping and not damaging the substrate. Summary of the Invention

[0004] The present invention is made in view of the above problems, and provides an electrolytic stripping formula and process for electroplating fixtures.

[0005] The first aspect of the present invention provides an electrolytic stripping formula for electroplating fixtures, which includes, by weight: 30-50 parts of sodium nitrate, 15-35 parts of ammonium nitrate, 15-30 parts of ammonium chloride, 15-25 parts of tartaric acid, and 10-20 parts of citric acid.

[0006] In some embodiments of the present invention, the purities of the sodium nitrate, the ammonium chloride, the tartaric acid, and the citric acid are industrial-grade chemical pure; and / or, the purity of the ammonium nitrate is analytical pure.

[0007] In some embodiments of the present invention, when the electrolytic stripping formula for electroplating fixtures is configured to be used as an electrolytic stripping solution, the dosage is 100 g / L to 120 g / L.

[0008] The second aspect of the present invention provides an electrolytic stripping process for electroplating fixtures, which includes the following steps:

[0009] Prepare an electrolytic stripping solution, and the electrolytic stripping solution includes the above formula;

[0010] Immerse the electroplating fixture workpiece in the electrolyte, and start electrolytic stripping under preset electrolytic conditions to obtain the stripped electroplating fixture.

[0011] In some embodiments of the present invention, the preset electrolytic conditions include setting the cathode material as 304 stainless steel.

[0012] In some embodiments of the present invention, the preset electrolytic conditions include setting the voltage to 4 V to 8 V.

[0013] In some embodiments of the present invention, the preset electrolysis conditions include setting the maximum temperature < 50°C.

[0014] In some embodiments of the present invention, the preset electrolysis conditions include setting the pH value to 5 - 7.

[0015] In some embodiments of the present invention, when the pH value ≥ 6.5 is detected during electrolysis, glacial acetic acid is added for adjustment.

[0016] In some embodiments of the present invention, by weight, the electrolytic stripping solution includes 35 parts of sodium nitrate, 20 parts of ammonium nitrate, 15 parts of ammonium chloride, 18 parts of tartaric acid, and 12 parts of citric acid.

[0017] Advantages achievable by the present invention:

[0018] The present invention provides an electrolytic stripping formula for an electroplating fixture. Among them, sodium nitrate and ammonium nitrate, as strong oxidants, rapidly destroy the metal coating (such as nickel and chromium) during electrolysis to accelerate its dissolution; ammonium chloride enhances the conductivity of the electrolyte, improves the current efficiency, and further shortens the stripping time; tartaric acid and citric acid form a weak acidic environment, chelating the dissolved metal ions (such as Fe 3+ , Ni 2+ ) to prevent their redeposition on the substrate surface, ensuring the continuous and efficient progress of the stripping reaction, extending the bath life. At the same time, the composite acid system of tartaric acid and citric acid has mild acidity and self-buffering ability, avoiding excessive corrosion of stainless steel or carbon steel substrates. Detailed implementation manners

[0019] The following description is provided to enable those skilled in the art to fully understand the present invention and is not intended to limit the subject matter recited in the claims.

[0020] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present invention, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] If there is no special instruction, all the embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0022] If there is no special instruction, all the technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0023] If there is no special instruction, all the steps of the present invention can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0024] In the field of electroplating processing, the traditional stripping process for electroplating fixtures faces the problem of being difficult to balance efficiency and substrate protection. Traditional chemical stripping methods, such as concentrated nitric acid oxidation method, anti-staining salt method, etc., have a long stripping time. Especially for fixtures with complex shapes, the stripping is not clean, while the electrolytic stripping method is likely to cause serious corrosion of the fixtures. Therefore, there is currently a lack of a method that can quickly strip and does not damage the substrate.

[0025] In view of this, this solution proposes an electrolytic stripping formula for electroplating fixtures, which includes, by weight: 30-50 parts of sodium nitrate, 15-35 parts of ammonium nitrate, 15-30 parts of ammonium chloride, 15-25 parts of tartaric acid, and 10-20 parts of citric acid.

[0026] Sodium nitrate and ammonium nitrate, as strong oxidants, rapidly destroy metal coatings (such as nickel and chromium) during electrolysis to accelerate their dissolution; ammonium chloride enhances the conductivity of the electrolyte, improves the current efficiency, and further shortens the stripping time; tartaric acid and citric acid form a weakly acidic environment, chelating the dissolved metal ions (such as Fe 3+ 、Ni 2+ ), preventing their re-deposition on the substrate surface, ensuring the continuous and efficient progress of the stripping reaction, and extending the life of the bath solution. At the same time, the composite acid system of tartaric acid and citric acid has mild acidity and self-buffering ability, avoiding excessive corrosion of stainless steel or carbon steel substrates.

[0027] In some embodiments, the purities of the sodium nitrate, the ammonium chloride, the tartaric acid, and the citric acid are industrial-grade chemical pure; and / or, the purity of the ammonium nitrate is analytical pure.

[0028] Chemical pure refers to the reagent purity that meets general production or analytical tests. The purity of analytical pure is higher than that of chemical pure and is generally used in places with more demanding requirements, such as reagents used in hospitals. Chromatographic pure refers to the standard reagent used in chromatographic analysis, and only the peaks of the specified compound appear under chromatographic conditions, without impurity peaks.

[0029] The price of industrial-grade reagents is only 1 / 5 to 1 / 3 of that of analytical pure. In this solution, by optimizing the formula and process, the oxidation-chelating system actively manages impurities instead of passively relying on reagent purity, and can significantly reduce production costs without affecting performance.

[0030] In some embodiments, when the electrolytic stripping formula for electroplating fixtures is configured to be used as an electrolytic stripping solution, the dosage is 100 g / L to 120 g / L. Preferably, the dosage of the electrolytic stripping formula for electroplating fixtures is 105 g / L to 115 g / L.

[0031] In some embodiments, the solvent of the electrolytic stripping solution is water, a mixture of water and sodium dodecyl sulfate, or a mixture of water and isopropyl alcohol.

[0032] In some embodiments, when the solvent is a mixture of water and isopropyl alcohol, it is used to accelerate the stripping of the coating and reduce foam generation, and the volume ratio of water to isopropyl alcohol is 95:5. In some embodiments, when the solvent is a mixture of water and sodium dodecyl sulfate, it is used to treat the coatings of fixtures with micropores or complex structures, and the volume ratio of water to sodium dodecyl sulfate is 98:2.

[0033] The second aspect of the present invention provides a preparation method for an electroplating fixture electrolytic stripping formula, comprising the following steps:

[0034] S1. Prepare an electrolytic stripping solution, which includes the above formula;

[0035] That is, the electrolytic stripping solution, by weight, includes: 30 - 50 parts of sodium nitrate, 15 - 35 parts of ammonium nitrate, 15 - 30 parts of ammonium chloride, 15 - 25 parts of tartaric acid, 10 - 20 parts of citric acid, and the formula dosage is 100 g / L - 120 g / L.

[0036] S2. Immerse the electroplating fixture workpiece in the electrolyte solution, and start electrolytic stripping under preset electrolytic conditions to obtain the stripped electroplating fixture.

[0037] In some embodiments, before "immersing the electroplating fixture workpiece in the electrolyte solution", the electroplating fixture workpiece is also pretreated for degreasing, including using an alkaline solution and ultrasonic degreasing. The ultrasonic frequency is 20 - 40 kHz, the temperature is 50°C - 80°C, and the degreasing time is 1 - 3 minutes.

[0038] During electrolytic stripping, the anode moves in the stripping tank to achieve the purpose of slightly stirring the electrolytic stripping solution, enhancing the mass transfer between the electrolyte solution and the coating surface, preventing the reaction stagnation caused by the local concentration gradient, further exerting the chemical activity advantage under low voltage, and air stirring is prohibited to avoid the mixing of oxygen and the resulting side reactions that affect the stripping effect. In some embodiments, the number of times the anode moves is 2 - 5 times per minute.

[0039] In some embodiments, the preset electrolytic conditions include setting the cathode material as 304 stainless steel. 304 stainless steel has good corrosion resistance and electrical conductivity, can effectively avoid the introduction of impurities, and at the same time maintain a high current efficiency.

[0040] In some embodiments, the preset electrolytic conditions include setting the voltage as 4 V - 8 V. In some actual operation cases, when the voltage is set to 10 V, the stripping rate is achieved, but slight pitting corrosion appears on the substrate. The lower voltage in this solution, in cooperation with technical features such as oxidants, conductive salts, chelating acids, temperature, and stirring, not only ensures the stripping speed but also avoids substrate damage caused by high voltage.

[0041] In some embodiments, the preset electrolytic conditions include setting the maximum temperature < 50°C. The anode movement breaks the diffusion layer limitation, accelerates the transfer of reactants and products, and in cooperation with low-temperature operation, stripping and unhooking at a lower temperature can maintain the activity and stability of the electrolyte solution, and reduce the volatilization of the electrolyte solution and save electrical energy. Materials such as PVC tank bodies and stainless steel cathodes have better corrosion resistance at low temperatures, reduce equipment aging and replacement frequency, extend equipment life, and greatly reduce production costs.

[0042] In some embodiments, the preset electrolysis conditions include setting the pH value to 5 - 7.

[0043] In some embodiments, when the pH value ≥ 6.5 is detected during electrolysis, glacial acetic acid is added for adjustment. At high pH (≥ 6.5), the oxidation potential of nitrate decreases, and the stripping efficiency drops significantly. Glacial acetic acid is pre-diluted with deionized water at a volume ratio of 1:5 - 1:10 to avoid excessive local concentration.

[0044] In some embodiments, by weight, the electrolytic stripping solution includes 35 parts of sodium nitrate, 20 parts of ammonium nitrate, 15 parts of ammonium chloride, 18 parts of tartaric acid, and 12 parts of citric acid. Under this stripping formulation, the most efficient and harmless stripping can be achieved.

[0045] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not used to limit the present invention.

[0046] Example 1

[0047] 35 parts of sodium nitrate (industrial grade, chemically pure), 20 parts of ammonium nitrate (analytical pure), 15 parts of ammonium chloride (industrial grade, chemically pure), 18 parts of tartaric acid (industrial grade, chemically pure), and 12 parts of citric acid (industrial grade, chemically pure) are mixed, and a solvent with a volume ratio of water to isopropanol of 95:5 is added to prepare a stripping solution with a concentration of 110 g / L. Among them, the purities of sodium nitrate, ammonium chloride, tartaric acid, and citric acid are industrial grade, chemically pure, ammonium nitrate is analytical pure, sodium nitrate is purchased from Guangdong Gaoli Group, ammonium chloride, tartaric acid, and citric acid are purchased from Shenzhen Huachuang Chemical Co., Ltd., and ammonium nitrate is purchased from Nanjing Nianshun Chemical Materials Co., Ltd.;

[0048] A PVC board is used to make a stripping tank with dimensions of 1.5 m × 0.8 m × 0.6 m (length × width × depth), and a 304 stainless steel plate with a thickness of 2 mm is installed as the cathode; the nickel-plated steel wire with a diameter ≤ 2 mm to be stripped is immersed in an alkaline degreaser with a pH of 10 - 12 under the conditions of an ultrasonic frequency of 40 kHz and a temperature of 60 °C for 3 minutes of degreasing. After drying, it is placed in the plating tank and immersed. The voltage is set to 5 V, the temperature ≤ 45 °C, and the initial pH value is 6.0 - 6.5 to start stripping. The anode moving device is started with a frequency of 3 times per minute, and the fixture is taken out after 8 minutes of electrification treatment. The pH value of the plating tank is monitored in real time. When it rises to 6.5, 20% by volume concentration of glacial acetic acid is added dropwise until pH = 5.5.

[0049] Example 2

[0050] The stripping solution formulation includes: 45 parts of sodium nitrate, 15 parts of ammonium nitrate, 30 parts of ammonium chloride, 20 parts of tartaric acid, and 20 parts of citric acid. The concentration of the stripping solution is 120 g / L, and the others refer to Example 1.

[0051] Example 3

[0052] The stripping solution formulation includes: 40 parts of sodium nitrate, 25 parts of ammonium nitrate, 30 parts of ammonium chloride, 20 parts of tartaric acid, and 20 parts of citric acid. The concentration of the stripping solution is 105 g / L, the stripping voltage is set at 4 V, and the other conditions refer to Example 1.

[0053] Example 4

[0054] The stripping solution formulation includes: 30 parts of sodium nitrate, 35 parts of ammonium nitrate, 20 parts of ammonium chloride, 15 parts of tartaric acid, and 20 parts of citric acid. The solvent of the stripping solution is water and sodium dodecyl sulfate with a volume ratio of 98:2. The concentration of the stripping solution is 100 g / L, and the other conditions refer to Example 1.

[0055] Example 5

[0056] The diameter of the nickel-plated steel wire to be stripped is greater than 2 mm, the stripping voltage is set at 8 V, and the other conditions refer to Example 1.

[0057] Comparative Example 1

[0058] The stripping solution formulation includes: 35 parts of sodium nitrate, 25 parts of ammonium nitrate, 10 parts of ammonium chloride, 20 parts of tartaric acid, and 20 parts of citric acid. The other conditions refer to Example 1.

[0059] Comparative Example 2

[0060] The concentration of the stripping solution is 130 g / L, and the other conditions refer to Example 1.

[0061] Comparative Example 3

[0062] The stripping voltage is set at 10 V, and the other conditions refer to Example 1.

[0063] Comparative Example 4

[0064] The purities of sodium nitrate, ammonium chloride, tartaric acid, citric acid, and ammonium nitrate are all of analytical grade and are purchased from Nanjing Nianshun Chemical Materials Co., Ltd. The other conditions refer to Example 1.

[0065] Performance test:

[0066] Measure the surface roughness (Ra), coating residue, stripping rate, and bath life of the stripped fixtures obtained in Examples 1 to 5 and Comparative Examples 1 to 4, and record the results in Table 1:

[0067] 1. The surface roughness (Ra) is measured using a white light interferometer Zygo NewView 9000. The test standard is ISO4287, the sampling length is 0.8 mm, and the evaluation length is 4 mm; the measurement positions are randomly selected at 5 points on the surface of the fixture, and the average value is taken.

[0068] 2. For the residual coating, use the Bruker S8 TIGER X-ray fluorescence spectrometer to measure the mass percentage of nickel (Ni) element on the surface of the substrate after stripping. The detection limit is 0.01%.

[0069] 3. Stripping rate: Use the Fischer MP0R eddy current thickness gauge to measure the coating thickness before and after stripping, and calculate the thickness removed per unit time (μm / min).

[0070] 4. Bath life: When the stripping rate drops to 70% of the initial value, or the precipitation amount exceeds 5% of the bath volume, it is regarded as invalid, and record the number of batches of stripped products.

[0071] Table 1: Test results of Examples 1-5 and Comparative Examples 1-4

[0072]

[0073] Examples 1 to 3 are preferred examples. Example 1 balances cost, efficiency, and substrate protection. Example 2 has the fastest stripping rate, but relatively high surface roughness, and is suitable for rapid treatment of thick coatings. Example 3 provides the best substrate protection, but has a slow speed and is suitable for precision parts.

[0074] In Comparative Example 1, poor conductivity leads to reduced efficiency and relatively high coating residue. In Comparative Example 2, the high concentration of stripping solution causes excessive corrosion, and the bath life is only 8 batches. In Comparative Example 3, a voltage of 10 volts causes substrate damage and the bath impurities increase and fail quickly. Comparative Example 4 is a stripping formula with all analytical pure components, having the best performance, but the cost increases by at least 50%.

[0075] Based on the above performance results, this solution provides an electrolytic stripping formula for electroplating fixtures. Among them, sodium nitrate and ammonium nitrate are used as strong oxidants to quickly destroy metal coatings (such as nickel and chromium) during electrolysis and accelerate their dissolution; ammonium chloride enhances the conductivity of the electrolyte, improves the current efficiency, and further shortens the stripping time; tartaric acid and citric acid form a weak acidic environment to chelate dissolved metal ions (such as Fe 3+ 、Ni 2+) To prevent its redeposition on the substrate surface, ensure the continuous and efficient progress of the stripping reaction, and extend the bath life. At the same time, the composite acid system of tartaric acid and citric acid has mild acidity and self-buffering ability, avoiding excessive corrosion of stainless steel or carbon steel substrates. By optimizing the formula and process, the oxidation-chelating system actively manages impurities instead of relying passively on reagent purity, and can significantly reduce production costs without affecting performance. It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same function and effect as the technical idea within the technical solution scope of the present invention are all included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that those skilled in the art can think of to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. An electrolytic stripping formula for an electroplating fixture, characterized in that, By weight, it includes: 30 to 50 parts of sodium nitrate, 15 to 35 parts of ammonium nitrate, 15 to 30 parts of ammonium chloride, 15 to 25 parts of tartaric acid, and 10 to 20 parts of citric acid.

2. The electroplating fixture electrolytic unhooking formula according to claim 1, characterized in that, The purities of the sodium nitrate, the ammonium chloride, the tartaric acid, and the citric acid are industrial-grade chemically pure; and / or, the purity of the ammonium nitrate is analytical pure.

3. The electroplating fixture electrolytic unhooking formula according to claim 1, characterized in that, When the electroplating fixture electrolytic stripping formula is configured to be used as an electrolytic stripping solution, the dosage is 100 g / L to 120 g / L.

4. An electrolytic unhooking process for an electroplating hanger, characterized in that, It includes the following steps: Prepare an electrolytic stripping solution, and the electrolytic stripping solution includes the formula described in any one of claims 1 to 3; Immerse the electroplating fixture workpiece in the electrolyte, and start electrolytic stripping under preset electrolytic conditions to obtain the electroplating fixture after stripping.

5. The electrolytic unhooking process of the electroplating hanger according to claim 4, characterized in that, The preset electrolytic conditions include setting the cathode material as 304 stainless steel.

6. The electroplating fixture electrolytic unhooking process according to claim 4, characterized in that, The preset electrolytic conditions include setting the voltage to 4 V to 8 V.

7. The electroplating fixture electrolytic unhooking process according to claim 4, characterized in that, The preset electrolytic conditions include setting the maximum temperature < 50 °C.

8. The electroplating fixture electrolytic unhooking process according to claim 4, characterized in that, The preset electrolytic conditions include setting the pH value to 5 to 7.

9. The electroplating fixture electrolytic unhooking process according to claim 8, characterized in that, When the pH value ≥ 6.5 is detected during electrolysis, glacial acetic acid is added for adjustment.

10. The electroplating fixture electrolytic unhooking process according to claim 4, characterized in that, By weight, the electrolytic stripping solution includes 35 parts of sodium nitrate, 20 parts of ammonium nitrate, 15 parts of ammonium chloride, 18 parts of tartaric acid, and 12 parts of citric acid.

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