Continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization

Abstract

The invention provides a continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization, which comprises the following steps: preparing a plating solution containing a main salt nickel sulfate, a reducing agent sodium hypophosphite, a complexing agent sodium citrate, a buffering agent and a crystallization inhibitor according to a preset concentration ratio, the crystallization inhibitor is one or more of a compound of organic polybasic phosphonate and nano titanium dioxide, a nitrogen-containing heterocyclic ring compound or a polymer with a comb-shaped structure; and the plating temperature, the pH value of the plating solution and the flow rate of the plating solution are controlled within a preset range, and continuous plating operation is conducted. The crystallization inhibitor is added into the plating solution components, and the crystallization inhibitor and metal ions such as Ni in the plating solution can form a complex and are uniformly dispersed, so that the nickel ion release speed is regulated and controlled, and local crystallization is avoided; in addition, the crystallization inhibitors can also provide a three-dimensional barrier effect and reduce dendritic crystal formation and abnormal growth of crystal grains, so that the effect of reducing crystallization of the plating solution is achieved, and the stability and production efficiency of the plating solution are improved.

Description

Technical Field

[0001] The present application belongs to the technical field of continuous high-phosphorus chemical nickel plating, and more specifically, to a continuous high-phosphorus chemical nickel plating method capable of reducing crystallization of plating solution. Background Art

[0002] In modern manufacturing, metal surface treatment is a key link to improve the performance of metal materials and expand their application range. Continuous chemical nickel plating, as an efficient and widely used surface treatment method, aims to give metal or non-metal substrates excellent properties such as corrosion resistance, hardness enhancement, and improved conductivity. However, traditional continuous chemical nickel plating technology faces many challenges in actual operation, especially the control of nickel crystallization and the stability of the plating solution, which are industry problems and seriously restrict the improvement of coating quality and production efficiency.

[0003] In the traditional continuous chemical nickel plating process, there are many factors that lead to the problem of crystallization of the plating solution. The proportion of each component in the plating solution is often not accurate enough. For example, when the main salt concentration is too high or fluctuates greatly, it is easy to form an oversaturated state in the plating solution, causing nickel ions to crystallize prematurely, thereby affecting the electroplating effect and the quality of the coating. At the same time, if the concentration of the reducing agent is not properly controlled, the chemical reaction in the plating solution will be unbalanced, triggering side reactions and generating some insoluble substances. These substances become the core of the crystallization of the plating solution and accelerate the crystallization process. In addition, the nickel plating process is a complex chemical reaction process, and there are many other known or unknown factors that will cause the crystallization of the plating solution and further affect the stability of the plating solution, thereby affecting the quality of the final coating and production efficiency. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a continuous high-phosphorus chemical nickel plating method that can reduce plating solution crystallization, so as to solve the technical problem of plating solution crystallization existing in the prior art and further affecting the stability of the plating solution.

[0005] To achieve the above object, the technical solution adopted in the present application is to provide a continuous high-phosphorus chemical nickel plating method that can reduce the crystallization of the plating solution, comprising the following steps: A plating solution comprising a main salt of nickel sulfate, a reducing agent of sodium hypophosphite, a complexing agent of sodium citrate, a buffer and a crystallization inhibitor is prepared according to a predetermined concentration ratio, wherein the crystallization inhibitor is one or more of a composite of an organic polyphosphonate and nano-titanium dioxide, a nitrogen-containing heterocyclic compound or a polymer having a comb-like structure; The plating temperature, the pH value of the plating solution and the flow rate of the plating solution are controlled within a preset range, and a continuous plating operation is performed.

[0006] In one embodiment, the crystallization inhibitor is a complex formed by grafting an organic polyphosphonate onto the surface of nano-titanium dioxide via a coupling agent.

[0007] In one embodiment, the crystallization inhibitor is an imidazole compound or a polycarboxylate ether polymer.

[0008] In one embodiment, the concentration of the crystallization inhibitor is 0.3-0.7 g / L.

[0009] In one embodiment, the buffer is sodium acetate, or the buffer is a composite buffer system of sodium citrate and sodium dihydrogen phosphate.

[0010] In one embodiment, the concentration of nickel sulfate is 28-32 g / L, the concentration of sodium hypophosphite is 22-26 g / L, the concentration of sodium citrate is 18-22 g / L, the buffer is sodium acetate and the concentration is 12-18 g / L, and the flow rate of the plating solution is 0.6-0.8 m / s.

[0011] In one embodiment, one or more of the following steps are also included: Regularly detecting the concentration of nickel sulfate in the plating solution by a concentration detector, and when the concentration of nickel sulfate deviates from a predetermined range, adjusting the concentration of nickel sulfate in the plating solution by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, and dynamic adjustment of the concentration of sodium hypophosphite; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from a predetermined range, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0012] In one embodiment, the following steps are also included: The solid particles in the plating solution are regularly filtered through a filter membrane in the filter device, wherein the pore size of the filter membrane is 0.2-0.5 μm.

[0013] In one embodiment, the following steps are also included: Regularly remove metal ion impurities from the plating solution through ion exchange resins; And / or, organic pollutants in the plating solution are regularly adsorbed by activated carbon.

[0014] In one embodiment, the following steps are also included: Periodically changing the bath flow rate and / or flow rate; Alternatively, the plating tank can be divided into zones, where the plating solution composition, pH value, temperature and flow rate in different zones are different and can circulate mutually.

[0015] Compared with the prior art, the continuous high-phosphorus chemical nickel plating method provided in the present application that can reduce the crystallization of the plating solution, by adding a crystallization inhibitor to the plating solution components, for example, a composite of an organic polyphosphonate and nano-titanium dioxide, a nitrogen-containing heterocyclic compound, or a polymer with a comb-like structure, the crystallization inhibitor can form a complex with metal ions such as Ni²⁺ in the plating solution and disperse it evenly, thereby regulating the release rate of nickel ions and avoiding local crystallization; these crystallization inhibitors can also provide a steric barrier effect, reduce dendrite formation and abnormal grain growth, thereby achieving the effect of reducing the crystallization of the plating solution, thereby improving the stability of the plating solution, and further improving the coating quality and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 A flow chart of a continuous high-phosphorus chemical nickel plating method that can reduce crystallization of the plating solution provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0019] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0022] A continuous high-phosphorus chemical nickel plating method that can reduce plating solution crystallization provided in an embodiment of the present application is now described. The continuous high-phosphorus chemical nickel plating method that can reduce plating solution crystallization comprises the following steps: A plating solution comprising a main salt of nickel sulfate, a reducing agent of sodium hypophosphite, a complexing agent of sodium citrate, a buffer and a crystallization inhibitor is prepared according to a predetermined concentration ratio, wherein the crystallization inhibitor is one or more of a composite of an organic polyphosphonate and nano-titanium dioxide, a nitrogen-containing heterocyclic compound or a polymer having a comb-like structure; The plating temperature, the pH value of the plating solution and the flow rate of the plating solution are controlled within a preset range, and a continuous plating operation is performed.

[0023] Specifically, a plating solution is prepared first, which mainly includes the main salt nickel sulfate, the reducing agent sodium hypophosphite, the complexing agent sodium citrate, the buffer and the crystallization inhibitor. The buffer can be sodium acetate, sodium citrate, sodium dihydrogen phosphate or other compounds. In addition, the plating solution can also include other auxiliary ingredients such as stabilizers, promoters, wetting agents, brighteners, etc.

[0024] The role of the crystallization inhibitor is mainly to inhibit the premature crystallization of nickel ions in the plating solution, or to inhibit the imbalance of the reaction during the electroplating process, reduce the generation of insoluble substances caused by some side reactions and the formation of crystal nuclei on the surface of insoluble substances.

[0025] One of the optional crystallization inhibitors is a complex of organic polyphosphonate and nano-titanium dioxide. Organic polyphosphonate is based on polyol or amine compound as the skeleton, through the phosphonate group (-PO 3 R) to form a multifunctional structure; for example, the molecular formula of polyol phosphate ester (PAPE) is PO 4 HR 1 R 2 . Nano-titanium dioxide has a high specific surface area and more active sites, and can be well dispersed in the plating solution. Organic polyphosphonates can be grafted onto the surface of nano-titanium dioxide through a coupling agent to obtain organic polyphosphonate-modified nano-titanium dioxide. After nano-titanium dioxide is modified with organic polyphosphonates, a hydrophilic and controllable coating is formed on the surface, which improves the dispersion stability in the plating solution and avoids coating defects caused by particle agglomeration. ‌‌ Organic polyphosphonates can form a hydrophilic coating layer on the surface of nano-titanium dioxide through their phosphonate groups (-PO 3R) forms a stable complex with metal ions (such as Ni²⁺, Cu²⁺) in the plating solution, reduces the concentration of free metal ions, and slows down the rate of crystal nucleation. Nano-titanium dioxide, with its high specific surface area and surface hydroxyl groups, adsorbs metal ions and by-products (such as bubbles), reduces local supersaturation, and inhibits non-uniform nucleation, thereby inhibiting crystallization.

[0026] Another optional crystallization inhibitor is nitrogen-containing heterocyclic compounds, such as imidazole compounds and triazole compounds. These compounds can form special coordination structures with nickel ions to prevent the aggregation and crystallization of nickel ions. At the same time, these compounds can adsorb metal ions and by-products (such as bubbles), reduce local supersaturation, and inhibit non-uniform nucleation, thereby inhibiting crystallization.

[0027] Another optional crystallization inhibitor is a polymer with a comb-like structure, such as carboxymethyl cellulose (CMC). The carboxylic acid group (-COO⁻) on the molecular chain forms a dynamic coordination bond with Ni²⁺, inhibiting the aggregation of crystal nuclei through the steric hindrance effect. The main chain of this type of polymer with a comb-like structure can form a dynamic complex with Ni²⁺, while the side chains provide steric barriers to reduce dendrite formation and abnormal grain growth.

[0028] In addition, the crystallization inhibitor can also be a complex of organic polyphosphonate and nano-titanium dioxide, nitrogen-containing heterocyclic compounds, or a polymer with a comb-like structure. For example, nitrogen-containing heterocyclic compounds and polymers with a comb-like structure can be added to the plating solution at the same time. Alternatively, a complex of organic polyphosphonate and nano-titanium dioxide and nitrogen-containing heterocyclic compounds can be added to the plating solution at the same time. In this way, the organic polyphosphonate can avoid local over-deposition by regulating the release rate of nickel ions; nitrogen-containing heterocyclic compounds as secondary reducing agents can also promote the redox efficiency of sodium hypophosphite and increase the deposition rate by 10-15%. ‌ After configuring the plating solution composition and concentration, the plating solution temperature, pH value and plating solution flow rate need to be adjusted within the predetermined range. For example, the plating solution temperature range is 88-92°C, the plating solution pH value needs to be maintained within the range of 4.5-5.5, and the plating solution flow rate needs to be controlled at 0.6-0.8m / s. Then the substrate to be plated can be placed in the plating solution for continuous plating operations.

[0029] In addition, before the substrate is continuously plated, the substrate may be pre-treated, such as degreasing, rust removal, and surface activation. After the electroplating is completed, post-treatment may be performed, such as cleaning and drying the coating to remove the residual solvent on the coating surface.

[0030] The continuous high-phosphorus chemical nickel plating method that can reduce the crystallization of the plating solution provided in the present application, by adding a crystallization inhibitor to the plating solution components, for example, a composite of an organic polyphosphonate and nano-titanium dioxide, a nitrogen-containing heterocyclic compound, or a polymer with a comb-like structure, the crystallization inhibitor can form a complex with metal ions such as Ni²⁺ in the plating solution and disperse it evenly, thereby regulating the release rate of nickel ions and avoiding local crystallization; these crystallization inhibitors can also provide a steric barrier effect, reduce dendrite formation and abnormal grain growth, thereby achieving the effect of reducing the crystallization of the plating solution, thereby improving the stability of the plating solution, and further improving the coating quality and production efficiency.

[0031] In one embodiment, the crystallization inhibitor is a composite formed by grafting an organic polyphosphonate onto the surface of nano-titanium dioxide via a coupling agent. The specific preparation process is as follows: Nano-titanium dioxide powder was added to deionized water and ultrasonically stirred for 30 minutes to form a uniformly dispersed suspension. The silane coupling agent was dissolved in anhydrous ethanol, and then the silane coupling agent solution was added to the nano-titanium dioxide suspension and stirred at 60°C for 3 hours to anchor the silane coupling agent on the surface of the nano-titanium dioxide. Finally, an organic polyphosphonate, such as polyol phosphate ester (PAPE), was dissolved in a buffer solution and added to the nano-titanium dioxide suspension modified with the silane coupling agent, and the covalent bonding of the phosphonate group and the coupling agent functional group was achieved through a condensation reaction, thereby achieving a grafting reaction of the organic polyol phosphonate.

[0032] The composite of organic polyphosphate and nano-titanium dioxide prepared by grafting reaction is an organic and inorganic hybrid. Both organic polyphosphate and nano-titanium dioxide can provide corresponding active sites for complexing with metal ions in the plating solution. In addition, nano-titanium dioxide has good dispersibility, which further reduces local supersaturation and inhibits non-uniform nucleation, thereby achieving the effect of inhibiting crystallization.

[0033] In one embodiment, the crystallization inhibitor is an imidazole compound. Imidazole compounds can form a special coordination structure with nickel ions through the strong coordination ability of their nitrogen-containing heterocyclic rings, form a stable complex with nickel ions, and prevent nickel ions from aggregating and crystallizing due to local supersaturation. Specifically, one or more of carbonyldiimidazole, benzimidazole, and benzoimidazole can be selected.

[0034] In one embodiment, the crystallization inhibitor is a polycarboxylate ether polymer. For example, a polycarboxylate-polyoxyethylene ether graft copolymer (PCE) can be used. The main chain of PCE is a polycarboxylic acid structure, and the side chain is connected to the polyoxyethylene segment (such as APEG, HPEG, TPEG, etc.) through an ether bond (—O—) to form a "comb-like" molecular structure. The polycarboxylate ether polymer forms a stable complex with nickel ions (Ni²⁺) through the carboxylic acid group. At the same time, its side chain prevents the aggregation and growth of nickel salt crystal nuclei through the steric hindrance effect, effectively inhibits the precipitation of crystals such as nickel phosphate in the plating solution, and ensures the long-term stability of the plating solution.

[0035] In one embodiment, the concentration of the crystallization inhibitor is 0.3-0.7 g / L. The crystallization inhibitor at this concentration can selectively adsorb on active sites where crystals may form in the plating solution, interfere with the crystallization process of nickel ions, and make it difficult for nickel ions to aggregate to form large crystalline particles, thereby effectively reducing the possibility of crystallization of the plating solution.

[0036] In one embodiment, the buffer is sodium acetate. 3 COONa) is used as a buffer, and the concentration is maintained at 12-18g / L. The buffer can more effectively maintain the stability of the pH value of the plating solution, provide a stable environment for the chemical reaction in the plating solution, and reduce the crystallization of the solution caused by pH fluctuations.

[0037] In one embodiment, the buffer is a composite buffer system of sodium citrate and sodium dihydrogen phosphate. The composite buffer system composed of sodium citrate and disodium hydrogen phosphate is used. Sodium citrate can provide additional complexing to further stabilize nickel ions, while disodium hydrogen phosphate can play a buffering role in different pH ranges, enhance the resistance of the plating solution to pH changes, maintain the stability of the plating solution during continuous high-phosphorus chemical nickel plating, and reduce the possibility of crystallization of the plating solution.

[0038] In one embodiment, the concentration of nickel sulfate is 28-32 g / L, the concentration of sodium hypophosphite is 22-26 g / L, the concentration of sodium citrate is 18-22 g / L, the buffer is sodium acetate and the concentration is 12-18 g / L, and the flow rate of the plating solution is 0.6-0.8 m / s.

[0039] The main salt nickel sulfate (NiSO 4 ・6H 2 The concentration of sodium hypophosphite (NaH 2 PO 2 ・H2 The concentration of citric acid (C O) is stable at 22 - 26g / L. The appropriate reducing agent concentration can ensure the smooth reduction reaction of nickel ions in the plating solution and avoid the imbalance of the plating solution caused by too fast or too slow reduction rate, which may lead to crystallization. 6 H 8 O 7 ・H 2 O) as a complexing agent, the concentration range is maintained at 18-22g / L. High concentration and stable complexing agent can more effectively form a stable complex with nickel ions, reduce the activity of nickel ions, and inhibit its crystallization tendency. Sodium acetate (CH 3 COONa) is used as a buffer, and the concentration is maintained at 12-18g / L. The buffer can more effectively maintain the stability of the pH value of the plating solution, provide a stable environment for the chemical reaction in the plating solution, and reduce the crystallization of the solution caused by pH fluctuations.

[0040] In addition, the instability of the plating solution flow rate is also an important cause of plating solution crystallization. If the plating solution flow rate is too slow, the heat and by-products generated in the plating solution cannot be discharged in time, and accumulate in local areas, resulting in uneven composition of the plating solution, which also creates conditions for plating solution crystallization. With the help of a circulating pump, the plating solution flow rate is controlled at 0.6 - 0.8m / s. The appropriate flow rate can ensure that the plating solution is evenly distributed in the plating tank, and the heat and by-products generated by the reaction are taken away in time, avoiding abnormal changes in the composition of the plating solution in local areas, and reducing the risk of plating solution crystallization. At the same time, according to the size and shape of the plating tank and the loading capacity of the workpiece, the power and flow rate of the circulating pump are reasonably adjusted to ensure the stability of the plating solution flow rate.

[0041] By precisely controlling the concentrations of the main salt nickel sulfate, the reducing agent sodium hypophosphite, the chelating agent sodium citrate and the buffering agent sodium acetate within the above ranges, the proportions of each component are rationally optimized and combined to fundamentally adjust the chemical composition and properties of the plating solution, reduce the crystallization tendency of nickel ions, and maintain the chemical balance of the plating solution; at the same time, reasonable control of the plating solution flow rate can avoid problems such as changes in the solubility of substances in the plating solution and imbalance in chemical reactions caused by fluctuations in process parameters, thereby effectively inhibiting the crystallization of the solution.

[0042] In one embodiment, the following steps are also included: regularly detecting the nickel sulfate concentration in the plating solution by a concentration detector, and when the nickel sulfate concentration deviates from a predetermined range, adjusting the nickel sulfate concentration in the plating solution by adding nickel sulfate or deionized water.

[0043] In traditional electroplating solutions, the proportions of various components are often not accurate enough. For example, as the continuous high-phosphorus chemical nickel plating reaction proceeds, the concentration of the main salt nickel sulfate will change. When the concentration of the main salt nickel sulfate is too high or fluctuates greatly, it is easy to form an oversaturated state in the plating solution, prompting nickel ions to crystallize out in advance, thereby affecting the electroplating effect and the quality of the coating. Based on this, the present application sets a concentration detector in the plating bath, and the concentration detector is used to regularly detect the concentration of the main salt nickel sulfate in the plating bath to monitor the concentration of the main salt; when the concentration of nickel sulfate is high, deionized water is added to the plating bath to reduce the concentration of nickel sulfate in the plating bath; when the concentration of nickel sulfate is low, nickel sulfate is added to the plating bath to increase the concentration of nickel sulfate in the plating bath. In this way, the concentration of nickel sulfate in the plating bath is regularly detected, and the concentration of nickel sulfate is adjusted to a predetermined range accordingly according to the detection results, thereby preventing the concentration of nickel sulfate from fluctuating greatly and causing nickel ions in the plating bath to crystallize out in advance.

[0044] In one embodiment, the method further includes the following steps: real-time monitoring of the nickel ion reduction rate and the change in the potential of the plating solution, and dynamic adjustment of the concentration of sodium hypophosphite.

[0045] If the concentration of the reducing agent sodium hypophosphite is not properly controlled, the chemical reaction in the plating solution will be unbalanced, triggering side reactions and generating some insoluble substances. These substances will become the core of the plating solution crystallization and accelerate the crystallization process of the plating solution.

[0046] By applying a cyclic voltage through a three-electrode system (working electrode, reference electrode, counter electrode), the current peak intensity of the nickel ion reduction reaction is monitored to directly reflect changes in the reduction rate. The ORP value of the plating solution is directly measured using a platinum electrode and a reference electrode (such as Ag / AgCl) to reflect the activity of sodium hypophosphite (reducing agent) and the nickel ion reduction process in real time. The three-electrode system and ORP sensor are integrated into a monitoring system. When the potential exceeds the set range (such as greater than 650 mV), it triggers the automatic addition of the reducing agent. ‌‌‌ By real-time monitoring of the reduction of nickel ions in the plating solution and the potential changes of the plating solution, the amount of sodium hypophosphite added is dynamically adjusted to maintain the stability of the reduction reaction in the plating solution.

[0047] In one embodiment, the temperature of the plating solution is adjusted by the heating device and the cooling device so that the temperature fluctuation does not exceed 1° C. based on the set value.

[0048] The unstable temperature of the plating solution is also an important cause of crystallization. When the temperature of the plating solution is too high and exceeds the appropriate range, the solubility of various substances in the plating solution changes, and some components may crystallize due to reduced solubility. Frequent temperature fluctuations will also interfere with the stability of the chemical reaction in the plating solution, leading to an increase in the crystallization of the plating solution.

[0049] By installing heating and cooling devices in the plating tank and using a high-precision temperature control system, the plating solution temperature is kept stable and accurate at 88-92°C, ensuring that the plating solution temperature fluctuates no more than 1°C based on the set value. Stable temperature can ensure the stability of the solubility of various substances in the plating solution, maintain the normal progress of chemical reactions, and greatly reduce the crystallization of the plating solution caused by temperature fluctuations.

[0050] In one embodiment, an online pH monitor is used to monitor the pH value of the plating solution in real time. When the pH value of the plating solution deviates from a predetermined range, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0051] The unstable pH value of the plating solution is also an important cause of crystallization. If the pH value deviates from the normal range, the effects of the complexing agent, buffer and other components in the plating solution will be affected, and the stability of nickel ions cannot be effectively maintained, making it easy for nickel ions to aggregate and crystallize.

[0052] Install a pH monitor and an automatic dosing system in the plating tank, and use the online pH monitor to monitor the pH value of the plating solution in real time during the electroplating process. Once the pH value of the plating solution deviates from the range of 4.5 - 5.5, immediately add an appropriate amount of sulfuric acid or sodium hydroxide solution through the automatic dosing system for adjustment. For example, when the pH value is higher than 5.5, add an appropriate amount of sulfuric acid solution to lower the pH value; when the pH value is lower than 4.5, add sodium hydroxide solution to increase the pH value. Through this real-time monitoring and precise adjustment, the pH value of the plating solution is maintained stable to prevent crystallization of the plating solution caused by abnormal pH value.

[0053] In one embodiment, the continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization further comprises the following steps: The solid particles in the plating solution are regularly filtered through a filter membrane in the filter device, wherein the pore size of the filter membrane is 0.2-0.5 μm.

[0054] Solid impurity particles in the plating solution, such as dust, metal debris, and insoluble substances generated by side reactions, will become the core of the plating solution crystallization if these impurities are not removed in time, thus accelerating the crystallization process. Therefore, a high-precision filter device is installed in the plating tank, and the filter device is equipped with a filter membrane with a pore size of 0.2-0.5μm to filter the plating solution regularly. In the continuous high-phosphorus chemical nickel plating process, the plating solution is filtered through a filter membrane with a pore size of 0.2-0.5μm every 8-12 hours to remove solid impurity particles in the plating solution, thereby reducing the crystallization phenomenon of the plating solution.

[0055] In one embodiment, the continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization further comprises the following steps: Regularly remove metal ion impurities from the plating solution through ion exchange resins; And / or, organic pollutants in the plating solution are regularly adsorbed by activated carbon.

[0056] As the electroplating process continues, the impurities in the plating solution gradually increase, such as metal ion impurities, organic pollutants, etc. These impurities will destroy the stability of the plating solution and reduce its ability to inhibit crystallization. Therefore, an ion exchange resin filter is installed in the plating tank, and the plating solution is passed through the ion exchange resin filter every 3-5 days to remove metal ion impurities in the plating solution, such as copper ions, iron ions, etc.

[0057] In addition, the plating solution may also contain organic pollutants, such as unreacted additives, organic by-products, etc., which will also cause the stability of the plating solution to decrease. An activated carbon adsorption column can be installed in the plating tank, and the plating solution can be passed through the activated carbon adsorption column regularly to remove organic pollutants in the plating solution. Through regular purification, the purity of the plating solution can be maintained and the possibility of crystallization of the plating solution can be reduced.

[0058] It should be noted that in the actual production process, both an ion exchange resin filter device and an activated carbon adsorption column can be installed in the plating tank. A combination of ion exchange and activated carbon adsorption can be used to regularly purify the plating solution to maintain the stability of the plating solution and reduce the possibility of crystallization of the plating solution.

[0059] In one embodiment, the continuous high-phosphorus chemical plating method capable of reducing plating solution crystallization further comprises the following steps: periodically changing the flow rate and / or flow rate of the plating solution. By periodically changing the flow rate and / or flow rate of the plating solution, i.e., the pulsed circulation mode of the plating solution, the local concentration balance in the plating solution is broken, the accumulation of impurities and heat is reduced, and thus the crystallization of the plating solution is suppressed.

[0060] In one embodiment, the continuous high-phosphorus chemical plating method that can reduce plating solution crystallization also includes the following steps: partitioning the plating tank, and the plating solution composition, pH value, temperature, and flow rate in different areas are different and mutually circulated.

[0061] According to the reaction characteristics of different areas in the plating tank, the plating tank is managed and circulated in different zones. The plating solution composition and plating solution pH value, temperature, flow rate and other process parameters of each zone are set differently according to the needs. The plating solutions in each zone of the plating tank form an inter-circulation system, so as to more accurately meet the electroplating needs and reduce the risk of plating solution crystallization. This method of plating solution zoning management and circulation requires corresponding modification of the plating tank structure and configuration of the corresponding control system to achieve it.

[0062] Embodiment 1

[0063] A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization comprises: The plating solution is prepared according to the main salt nickel sulfate 30g / L, sodium hypophosphite 25g / L, sodium citrate 20g / L, sodium acetate 20g / L and PAPE modified nano titanium dioxide 0.5g / L; The plating temperature was controlled at 90°C (±1°C), the pH value of the plating solution was 5, the flow rate of the plating solution was 0.8 m / s, and the substrate was placed in the plating solution for continuous plating, and the time when turbid crystals appeared in the plating solution was recorded; The nickel sulfate concentration in the plating solution is regularly tested by a concentration detector. When the nickel sulfate concentration deviates from 28 - 32 g / L, the nickel sulfate concentration in the plating solution is adjusted by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, dynamically adjusting the concentration of sodium hypophosphite to maintain at 22 - 26 g / L; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value of 90°C; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from 4.5 - 5.5, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0064] Embodiment 2

[0065] A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization comprises: The plating solution is prepared according to the main salt of nickel sulfate 30g / L, sodium hypophosphite 25g / L, sodium citrate 20g / L, sodium acetate 20g / L and carbonyl diimidazole 0.5g / L; The plating temperature was controlled at 90°C (±1°C), the pH value of the plating solution was 5, the flow rate of the plating solution was 0.8 m / s, and the substrate was placed in the plating solution for continuous plating, and the time when turbid crystals appeared in the plating solution was recorded; The nickel sulfate concentration in the plating solution is regularly tested by a concentration detector. When the nickel sulfate concentration deviates from 28 - 32 g / L, the nickel sulfate concentration in the plating solution is adjusted by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, dynamically adjusting the concentration of sodium hypophosphite to maintain at 22 - 26 g / L; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value of 90°C; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from 4.5 - 5.5, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0066] Embodiment 3

[0067] A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization comprises: The plating solution is prepared according to the main salt of nickel sulfate 30g / L, sodium hypophosphite 25g / L, sodium citrate 20g / L, sodium acetate 20g / L and PCE 0.5g / L; The plating temperature was controlled at 90°C (±1°C), the pH value of the plating solution was 5, the flow rate of the plating solution was 0.8 m / s, and the substrate was placed in the plating solution for continuous plating, and the time when turbid crystals appeared in the plating solution was recorded; The nickel sulfate concentration in the plating solution is regularly tested by a concentration detector. When the nickel sulfate concentration deviates from 28 - 32 g / L, the nickel sulfate concentration in the plating solution is adjusted by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, dynamically adjusting the concentration of sodium hypophosphite to maintain at 22 - 26 g / L; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value of 90°C; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from 4.5 - 5.5, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0068] Comparative Example

[0069] A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization comprises: Prepare the plating solution according to the main salt of nickel sulfate 30g / L, sodium hypophosphite 25g / L, sodium citrate 20g / L, and sodium acetate 20g / L; The plating temperature was controlled at 90°C (±1°C), the pH value of the plating solution was 5, the flow rate of the plating solution was 0.8 m / s, and the substrate was placed in the plating solution for continuous plating, and the time when turbid crystals appeared in the plating solution was recorded; The nickel sulfate concentration in the plating solution is regularly tested by a concentration detector. When the nickel sulfate concentration deviates from 28 - 32 g / L, the nickel sulfate concentration in the plating solution is adjusted by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, dynamically adjusting the concentration of sodium hypophosphite to maintain at 22 - 26 g / L; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value of 90°C; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from 4.5 - 5.5, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

[0070] After continuous plating according to the steps of the above three embodiments and comparative examples, the recorded plating solution became turbid and crystallized, and the time when the stability began to decrease was 80h, 83h, 86h, and 78h respectively. The results are shown in Table 1: Table 1 Experimental data of plating solution stability of three embodiments and comparative examples Serial number Types of crystallization inhibitors Crystallization inhibitor concentration (g / L) pH value Bath temperature (°C) Crystallization time (h) Example 1 PAPE modified nano titanium dioxide 0.5 5 90 80 Example 2 Carbonyldiimidazole 0.5 5 90 83 Example 3 PCE 0.5 5 90 86 Comparative Example none none 5 90 78 From the above data, it can be seen that in the comparative example, since no crystallization inhibitor was added, nickel ions aggregated to form crystal nuclei the fastest, resulting in turbid crystallization of the plating solution in a short period of time. In Example 2, carbonyl diimidazole was used as a crystallization inhibitor. Since the molecular weight of carbonyl diimidazole was smaller than that of the crystallization inhibitors in Example 1 and Example 3, the inhibitory effect on the crystallization of the plating solution was slightly weaker. In Example 1, PAPE-modified nano-titanium dioxide was used as a crystallization inhibitor, which delayed the growth of crystal nuclei through physical adsorption and steric hindrance, and the nanostructure provided long-term dispersion. In Example 3, PCE was used as a crystallization inhibitor. PCE wrapped nickel ions through strong adsorption, and used polyethylene oxide side chains to form steric hindrance, which significantly inhibited the formation and growth of crystal nuclei, and the polymer chain had high stability, was resistant to high temperature and pH fluctuations, and had the best dispersion effect. Therefore, the plating solution had the strongest stability and the longest time for turbid crystallization to occur. It can be seen that the present application can significantly prolong the time for turbid crystallization to occur in the plating solution and improve the stability of the plating solution by adding a crystallization inhibitor to the plating solution.

[0071] In summary, the present application provides a new plating solution formula and supporting process in a continuous chemical nickel plating process. Through a precise formula, the chemical composition and properties of the plating solution are fundamentally adjusted. By adding a crystallization inhibitor, the crystallization tendency of nickel ions is reduced to maintain the chemical balance of the plating solution. Secondly, through a high-precision temperature control system, a pH value monitoring and adjustment system, and a reasonable plating solution flow rate control, it is ensured that the temperature, pH value and flow rate of the plating solution are always maintained within an appropriate and stable range during the electroplating process, avoiding problems such as changes in the solubility of substances in the plating solution and imbalance in chemical reactions caused by fluctuations in process parameters, thereby effectively inhibiting the crystallization of the plating solution. Finally, through continuous impurity removal and plating solution maintenance, regular filtration and purification treatment are performed to promptly remove solid particles, ionic impurities and organic pollutants in the plating solution, maintain the purity of the plating solution, prevent these substances from becoming the core of plating solution crystallization, extend the service life of the plating solution, maintain the stability of the plating solution, and reduce the crystallization phenomenon of the plating solution during continuous chemical high-phosphorus nickel plating. The technical solution of the present application effectively overcomes the shortcomings of the existing technology by precisely controlling the key elements in the electroplating process, achieves the goal of reducing nickel crystallization, improving the quality of the coating and the stability of the plating solution, and provides a high-performance, high-stability continuous chemical nickel electroplating solution for many industries with strict requirements on metal surface properties, such as electronics, mechanical manufacturing, aerospace, etc.

[0072] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A continuous high-phosphorus chemical nickel plating method capable of reducing crystallization of a plating solution, characterized in that: The following steps are involved: A plating solution comprising a main salt of nickel sulfate, a reducing agent of sodium hypophosphite, a complexing agent of sodium citrate, a buffer and a crystallization inhibitor is prepared according to a predetermined concentration ratio, wherein the crystallization inhibitor is one or more of a composite of an organic polyphosphonate and nano-titanium dioxide, a nitrogen-containing heterocyclic compound or a polymer having a comb-like structure; The plating temperature, the pH value of the plating solution and the flow rate of the plating solution are controlled within a preset range, and a continuous plating operation is performed.

2. The continuous high-phosphorus chemical nickel plating method for reducing plating solution crystallization as claimed in claim 1, characterized in that: The crystallization inhibitor is a complex formed by grafting an organic polyphosphonate onto the surface of nano titanium dioxide through a coupling agent.

3. The continuous high-phosphorus chemical nickel plating method for reducing plating solution crystallization as claimed in claim 1, characterized in that: The crystallization inhibitor is an imidazole compound or a polycarboxylate ether polymer.

4. The continuous high-phosphorus chemical nickel plating method for reducing plating solution crystallization as claimed in claim 1, characterized in that: The concentration of the crystallization inhibitor is 0.3-0.7 g / L.

5. The continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization as claimed in claim 1, characterized in that: The buffer is sodium acetate, or the buffer is a composite buffer system of sodium citrate and sodium dihydrogen phosphate.

6. A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization as claimed in any one of claims 1 to 4, characterized in that: The concentration of the nickel sulfate is 28-32 g / L, the concentration of the sodium hypophosphite is 22-26 g / L, the concentration of the sodium citrate is 18-22 g / L, the buffer is sodium acetate and the concentration is 12-18 g / L, and the flow rate of the plating solution is 0.6-0.8 m / s.

7. A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization as claimed in any one of claims 1 to 5, characterized in that: It also includes one or more of the following steps: Regularly detecting the concentration of nickel sulfate in the plating solution by a concentration detector, and when the concentration of nickel sulfate deviates from a predetermined range, adjusting the concentration of nickel sulfate in the plating solution by adding nickel sulfate or deionized water; Real-time monitoring of nickel ion reduction rate and bath potential changes in the plating solution, and dynamic adjustment of the concentration of sodium hypophosphite; The bath temperature is adjusted by the heating device and the cooling device so that the fluctuation does not exceed 1°C based on the set value; The pH value of the plating solution is monitored in real time using an online pH monitor. When the pH value of the plating solution deviates from a predetermined range, sulfuric acid or sodium hydroxide solution is added to the plating solution through a dosing system to adjust the pH value of the plating solution.

8. A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization as claimed in any one of claims 1 to 5, characterized in that: The following steps are also included: Solid particles in the plating solution are regularly filtered through a filter membrane in the filter device, wherein the pore size of the filter membrane is 0.2-0.5 μm.

9. A continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization as claimed in any one of claims 1 to 5, characterized in that: The following steps are also included: Regularly remove metal ion impurities from the plating solution through ion exchange resins; And / or, organic pollutants in the plating solution are regularly adsorbed by activated carbon.

10. The continuous high-phosphorus chemical nickel plating method capable of reducing plating solution crystallization according to any one of claims 1 to 5, characterized in that: The following steps are also included: Periodically changing the bath flow rate and / or flow rate; Alternatively, the plating tank can be divided into zones, where the plating solution composition, pH value, temperature and flow rate in different zones are different and can circulate mutually.

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