High-dispersity plastic bathroom electroplating chemical nickel liquid and process thereof

Abstract

The invention relates to the technical field of surface treatment, and discloses a high-dispersity plastic bathroom electroplating chemical nickel liquid which comprises the following components in parts by mass: 30-40 parts of nickel sulfate; 25 to 35 parts of sodium hypophosphite; 5-8 parts of a complexing agent composed of malic acid and succinic acid; 0.1 to 0.3 part of a stabilizing agent; 0.05 to 0.1 part of a surfactant; the complexing agent is composed of malic acid and succinic acid, and the mass ratio of the malic acid to the succinic acid is (1.5-2.5): 1; the stabilizing agent is cerous nitrate, the particle size of the cerous nitrate is 10-50nm, and the cerous nitrate is dispersed in the plating solution in the form of nano sol; the surface active agent is sophorolipid, the purity of the surface active agent is 95%-99%, and the critical micelle concentration of the sophorolipid is 0.05-0.1 part; the chemical nickel liquid further comprises a dispersing agent, wherein the dispersing agent is nano silicon dioxide modified by a silane coupling agent. Through real-time monitoring and gradient supplementing technologies, the chemical proportion of a reducing agent and a stabilizing agent in the plating solution is dynamically balanced, uniform deposition of nickel ions is ensured, and the effective life of the plating solution is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment, and specifically to a high-dispersibility plastic sanitary ware electroplating electroless nickel plating solution and its process. Background Art

[0002] Electroless nickel plating technology is widely used in the surface metallization treatment of plastic sanitary ware due to its excellent throwing power and corrosion resistance. However, the inherent hydrophobicity and chemical inertness of plastic substrates lead to insufficient coating adhesion, and the plating solution has complex components and poor stability, which easily causes defects such as coating oxidation and high porosity. In addition, the dependence on heavy metal catalysts (such as Sn / Pd) in traditional processes and the high pollution of the roughening step make it difficult to meet the increasingly strict environmental protection requirements.

[0003] In the prior art, plastic electroless nickel plating mostly adopts schemes such as fixed addition of sodium hypophosphite, mechanical roughening combined with Sn / Pd sensitization and activation. For example, by manually monitoring the pH value or nickel ion concentration of the plating solution and regularly adding reducing agents to maintain the deposition reaction; or using sulfuric acid single acid etching combined with palladium colloid catalysis to achieve surface metallization of the substrate. Although such processes can achieve basic functions, the maintenance of the plating solution depends on empirical judgment, and roughening and activation are carried out step by step, resulting in a long process.

[0004] However, the above methods have significant limitations: the traditional plating solution addition strategy cannot respond to the dynamic changes of chemical equilibrium in real time. Fixed addition is likely to cause local excess or depletion of sodium hypophosphite, resulting in imbalance of plating solution components (such as inactivation of stabilizers and accumulation of by-products), thereby shortening the life of the plating solution and inducing problems such as coating oxidation and dendrite growth. The lag of manual intervention further amplifies the concentration fluctuation, making it difficult to meet the strict requirements of precision sanitary ware for coating uniformity and durability. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a high-dispersibility plastic sanitary ware electroplating electroless nickel plating solution and its process, which solves the problems of poor coating adhesion, short plating solution life and environmental pollution caused by the instability of the dynamic equilibrium of the traditional plastic electroless nickel plating process.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-dispersibility plastic sanitary ware electroplating electroless nickel plating solution includes the following components in mass fractions: Nickel sulfate: 30 - 40 parts; Sodium hypophosphite: 25 - 35 parts; Complexing agent: 5 - 8 parts, composed of malic acid and succinic acid; Stabilizer: 0.1 - 0.3 parts; Surfactant: 0.05 - 0.1 part; pH regulator: 1 - 5 parts.

[0007] Preferably, the complexing agent consists of malic acid and succinic acid, and the mass ratio of the two is (1.5 - 2.5):1.

[0008] Preferably, the stabilizer is cerium nitrate, the particle size of the cerium nitrate is 10 - 50 nm, and it is dispersed in the plating solution in the form of a nano-sol.

[0009] Preferably, the surfactant is sophorolipid, its purity is 95% - 99%, the addition amount is 0.05 - 0.1 parts, and the critical micelle concentration of the sophorolipid is 0.05 - 0.1 parts.

[0010] Preferably, the electroless nickel plating solution further contains a dispersant: Dispersant: nano-silica modified with silane coupling agent, the specific surface area of the nano-silica is 200 - 300 m 2 / g, and the pore size is 2 - 5 nm.

[0011] The present invention also provides a preparation process for an electroless nickel plating solution for high-dispersibility plastic sanitary ware electroplating, including the following steps: Step 1. Substrate pretreatment: The plastic substrate is surface-roughened with an acidic roughening solution. Step 2. Plasma activation: The roughened substrate is subjected to plasma treatment in a mixed gas containing oxygen. Step 3. Electroless nickel plating: The activated substrate is immersed in the electroless nickel plating solution, maintaining the plating solution temperature at 50 - 60 °C, and the reducing agent and stabilizer are monitored and replenished in real time during the plating process. Step 4. Post-electroplating treatment: The nickel-plated substrate is subjected to copper plating and chromium plating treatment.

[0012] Preferably, the specific operation of Step 1 includes: The plastic substrate is immersed in an environmentally friendly roughening solution, which consists of sulfuric acid, hydrogen peroxide, oxalic acid, and polydopamine, the roughening temperature is 40 - 50 °C, and the time is 15 - 20 minutes; After roughening, it is washed with water and dried.

[0013] Preferably, the specific operation of Step 2 includes: The roughened substrate is placed in a pulsed radio frequency glow discharge device, and a mixed gas of argon and oxygen with a volume ratio of 9:1 is introduced; Set the radio frequency power to 200 - 250 W, the pulse frequency to 10 kHz, the duty cycle to 30%, and the treatment time to 8 - 10 minutes; After treatment, it is directly subjected to electroless nickel plating without sensitization or activation in separate steps.

[0014] Preferably, the specific operation of Step 3 includes: During electroless nickel plating, the molar ratio of complexing agent to stabilizer is monitored in real time by an on-line conductivity sensor, and the ratio is maintained at 2:1 ± 10%; When the molar ratio deviates, sodium hypophosphite solution is added at a rate of 1-2 mL / min.

[0015] Preferably, the specific operation of step four includes: Copper plating treatment: current density 2-3 A / dm 2 , time 15 minutes, and the plating solution is a copper sulfate system; Chromium plating treatment: current density 10-15 A / dm 2 , time 5 minutes, and the plating solution is a hexavalent chromium system; After plating, wash with water and dry.

[0016] The present invention provides a high-dispersibility plastic bathroom electroplating electroless nickel solution and its process. It has the following beneficial effects: 1. Through real-time monitoring and gradient addition technology, the present invention dynamically balances the chemical ratio of reducing agent and stabilizer in the plating solution. Compared with traditional fixed addition or manual regulation schemes, it solves the problems of plating solution instability and coating oxidation caused by concentration fluctuations, ensures uniform deposition of nickel ions, and significantly extends the effective life of the plating solution.

[0017] 2. Based on the one-step activation method of argon-oxygen mixed plasma, the present invention synchronously realizes surface roughening and anchoring of polar groups. Compared with traditional processes relying on Sn / Pd catalysis, it avoids heavy metal pollution and deterioration of bonding strength caused by uneven distribution of palladium particles, and at the same time reduces the generation of high-COD wastewater, taking into account both high efficiency and environmental protection.

[0018] 3. By surface chemically modifying nanomaterials, the present invention inhibits their non-specific aggregation in the plating solution. Compared with the direct addition scheme of unmodified nanoparticles, it solves the problems of increased coating porosity and decreased mechanical properties caused by particle aggregation, and significantly improves the density and wear resistance of the coating.

[0019] 4. The present invention adopts a roughening system of H2O2 synergistic acid etching to strip the surface passivation layer through free radical oxidation. Compared with single acid etching processes, it overcomes the problems of insufficient roughening depth and metal salt dissolution pollution, ensures uniform coating coverage on complex structure surfaces, and at the same time reduces the difficulty of subsequent wastewater treatment. Description of the Drawings

[0020] Figure 1 It is a three-dimensional view of the present invention. Detailed Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] An embodiment of the present invention provides a highly dispersible electroless nickel plating solution for plastic sanitary ware, which comprises the following components in parts by mass: Nickel sulfate: 30 - 40 parts; Sodium hypophosphite: 25 - 35 parts; Complexing agent: 5 - 8 parts, composed of malic acid and succinic acid; Stabilizer: 0.1 - 0.3 parts; Surfactant: 0.05 - 0.1 part; pH regulator: 1 - 5 parts.

[0023] The complexing agent is composed of malic acid and succinic acid, and the mass ratio of the two is (1.5 - 2.5):1.

[0024] The stabilizer is cerium nitrate, the particle size of cerium nitrate is 10 - 50 nm, and it is dispersed in the plating solution in the form of a nano sol.

[0025] The surfactant is sophorolipid, its purity is 95% - 99%, and the addition amount is 0.05 - 0.1 part. The critical micelle concentration of sophorolipid is 0.05 - 0.1 part.

[0026] The electroless nickel plating solution further contains a dispersant: Dispersant: nano - silica modified with a silane coupling agent, the specific surface area of the nano - silica is 200 - 300 m 2 / g, and the pore size is 2 - 5 nm.

[0027] The preparation process of a highly dispersible electroless nickel plating solution for plastic sanitary ware described below can be mutually referred to with the highly dispersible electroless nickel plating solution for plastic sanitary ware described above.

[0028] Please refer to the attached Figure 1 , a preparation process of a highly dispersible electroless nickel plating solution for plastic sanitary ware, comprising the following steps: Step 1, pretreatment of the substrate: The plastic substrate is surface - roughened with an acidic roughening solution; Step 2, plasma activation: The roughened substrate is subjected to plasma treatment in a mixed gas containing oxygen; Step 3, electroless nickel plating: The activated substrate is immersed in the electroless nickel plating solution, maintaining the plating solution temperature at 50 - 60 °C, and the reducing agent and stabilizer are monitored and replenished in real time during the plating process; Step 4. Post-plating treatment: The nickel-plated substrate is subjected to copper plating and chromium plating treatments.

[0029] The specific operations of Step 1 include: Immerse the plastic substrate in an environmentally friendly roughening solution composed of sulfuric acid, hydrogen peroxide, oxalic acid, and polydopamine. The roughening temperature is 40 - 50 °C, and the time is 15 - 20 minutes; After roughening, wash with water and dry.

[0030] The specific operations of Step 2 include: Place the roughened substrate in a pulsed radio frequency glow discharge device, and introduce a mixed gas of argon and oxygen with a volume ratio of 9:1; Set the radio frequency power to 200 - 250 W, the pulse frequency to 10 kHz, the duty cycle to 30%, and the treatment time to 8 - 10 minutes; After treatment, directly perform electroless nickel plating without sensitization or activation steps.

[0031] The specific operations of Step 3 include: During electroless nickel plating, the molar ratio of the complexing agent to the stabilizer is monitored in real time by an on-line conductivity sensor, and the ratio is maintained at 2:1 ± 10%; When the molar ratio deviates, add sodium hypophosphite solution at a rate of 1 - 2 mL / min.

[0032] The specific operations of Step 4 include: Copper plating treatment: The current density is 2 - 3 A / dm 2 , the time is 15 minutes, and the plating solution is a copper sulfate system; Chromium plating treatment: The current density is 10 - 15 A / dm 2 , the time is 5 minutes, and the plating solution is a hexavalent chromium system; After plating, wash with water and dry.

[0033] In this embodiment, the specific operations of the substrate pretreatment include roughening solution preparation, substrate immersion treatment, and post-cleaning process. Generally, the roughening solution is compounded by sulfuric acid, hydrogen peroxide, oxalic acid, and polydopamine in specific proportions. As an option, the mass concentration of sulfuric acid is 30%, hydrogen peroxide is 5%, oxalic acid is 8%, and polydopamine is 0.1%. After the components are mixed evenly at 40 - 50 °C, a stable etching system is formed.

[0034] Specifically, the synergistic mechanism of the roughening solution is as follows: Sulfuric acid provides a high concentration of H + (pH ≈ 0.8), and dissolves the inorganic fillers (such as glass fibers) in the plastic substrate through protonation reaction; Hydrogen peroxide decomposes in an acidic environment to generate hydroxyl radicals (OH, reaction formula: H2O2 + H+ → H3O + + OH), directionally oxidize the hydrocarbon chains on the substrate surface to form micron-sized etching pits (depth 0.5 - 1.2 μm); Oxalic acid acts as a chelating agent and forms complexes (such as Al(C2O4)3 3+ , Ca 2+ ), logK = 16.5) with the dissolved metal ions (such as Al 3- ) to prevent secondary deposition from clogging the etching pits; Polydopamine adsorbs on the plastic surface through phenolic hydroxyl groups, preferentially etches the amorphous region and forms local hydrophilic sites (contact angle decreases from 95° to 45°).

[0035] In a possible implementation, the roughening temperature is set to 45 ± 5°C, and the treatment time is 15 - 20 minutes. If the temperature is lower than 40°C, the etching rate drops significantly (<0.1 mg / cm 2 ·min), resulting in insufficient micro-pit density; if it is higher than 50°C, the self-decomposition of hydrogen peroxide intensifies (half-life < 10 min), and the roughening uniformity deteriorates (SEM shows that the dispersion of the etching pit depth is ±0.5 μm).

[0036] In this embodiment, the specific operations of plasma activation include gas atmosphere regulation, radio frequency power loading, and surface modification treatment. Generally, a pulsed radio frequency glow discharge device is used, and a mixed gas of argon and oxygen (volume ratio 9:1) is introduced. The radio frequency power is set to 200 - 250 W, the pulse frequency is 10 kHz, the duty cycle is 30%, and the treatment time is 8 - 10 minutes. As an option, the purity of argon in the mixed gas is ≥99.99%, and the purity of oxygen is ≥99.5% to prevent impurity gases (such as N2) from participating in the reaction to generate nitrogen oxides (such as NO2 - ), causing surface passivation.

[0037] Specifically, the action path of plasma activation is divided into two mechanisms: physical bombardment and chemical oxidation: Physical bombardment: Argon ions (Ar + ) obtain kinetic energy ≥ 5 eV under the acceleration of the electric field and impact the substrate surface to form micron-sized pits with Ra ≈ 0.5 μm (AFM test data), increasing the mechanical interlocking sites; Chemical oxidation: Oxygen dissociates into oxygen free radicals (O + , O2 + , reaction formula: e - + O2 → 2O + +3e - ) under the collision of high-energy electrons and reacts with the carbon chains on the plastic surface to generate polar groups such as —COOH and —OH (XPS quantitative coverage rate ≥ 85%).

[0038] In a possible implementation, the radio frequency power needs to be strictly controlled within the range of 200 - 250 W. If the power is lower than 200 W, the density of oxygen free radicals is insufficient (the mass spectrometry detects that the O + signal intensity < 10 3 counts / s), resulting in a polar group coverage rate < 40%; if it is higher than 250 W, the temperature rise on the substrate surface exceeds 120 °C (monitored by an infrared thermal imager), causing thermal deformation (warpage amount ≥ 0.5 mm / m). In this embodiment, the specific operations of electroless nickel plating include plating solution preparation, dynamic replenishment control, and deposition process monitoring. Generally, the temperature of the plating solution is maintained at 50 - 60 °C, and the plating time is adjusted according to the required coating thickness (usually 8 - 12 minutes). As an option, the plating solution contains nickel sulfate (30 - 40 parts), sodium hypophosphite (25 - 35 parts), malic acid - succinic acid complexing agent (5 - 8 parts, ratio 1.5 - 2.5:1), cerium nitrate stabilizer (0.1 - 0.3 parts), and sophorolipid surfactant (0.05 - 0.1 parts). After mixing the components in deionized water, ultrasonic dispersion is carried out for 30 minutes (frequency 40 kHz).

[0039] Specifically, the dynamic replenishment control is achieved through an on - line conductivity sensor. The sensor monitors the molar ratio of the complexing agent (malic acid + succinic acid) to the stabilizer (cerium nitrate) in real - time. When the detected ratio deviates from 2:1 ± 10%, the PLC system triggers the sodium hypophosphite replenishment pump. The replenishment rate is set at 1 - 2 mL / min.

[0040] In a possible implementation, the temperature of the plating solution is precisely controlled at 55 ± 2 °C. When the temperature is lower than 50 °C, the reduction rate of nickel ions decreases (deposition rate < 8 μm / h), and the denseness of the coating deteriorates (porosity > 5%); when it is higher than 60 °C, the self - decomposition of sodium hypophosphite intensifies (decomposition rate > 0.12 min -1 ), and the stability of the plating solution decreases (service life < 5 MTO).

[0041] In this embodiment, the specific operations of post - electroplating treatment include copper plating, chromium plating, and post - cleaning processes. Generally, copper plating uses a copper sulfate system, and chromium plating uses a hexavalent chromium system. Parameters such as current density and time are regulated step - by - step according to the functional requirements of the coating. As an option, the copper plating solution contains copper sulfate (Cu 2+ 25 g / L), sulfuric acid (H2SO4 50 g / L), and brightening agent (polyethylene glycol 0.1 g / L), and the chromium plating solution contains chromic anhydride (CrO3 250 g / L), sulfuric acid (H2SO4 2.5 g / L), and catalyst (SrSO4 0.5 g / L). Specifically, copper plating treatment serves as an intermediate layer, and its functions include: Filling micropores: The porosity of the electroless nickel plating layer surface ≤ 1.2% (image analysis data), and the copper plating solution further seals the pores (pressing the porosity to 0.3%) through high leveling additives (such as thiourea derivatives); Stress buffering: The ductility of the copper layer (elongation rate ≥ 25%) can relieve the difference in thermal expansion coefficients between the nickel and chromium layers ( = 4.5×10 -6 / ℃), preventing interface cracking.

[0042] Example 1: Formulation components (per 100L of plating solution): Nickel sulfate: 35 parts (i.e., 35 kg, corresponding concentration 35 g / L); Sodium hypophosphite: 30 parts (30 kg, initial concentration 30 g / L, dynamically replenished to 35 g / L); Complexing agent: 4.2 parts of malic acid + 1.8 parts of succinic acid (total 6 parts, mass ratio 2.3:1); Stabilizer: 0.2 parts (0.2 kg) of cerium nitrate nanosol (particle size 20 nm); Surfactant: 0.08 parts (0.08 kg) of sophorolipid (purity 98%); pH regulator: 3 parts of ammonia water (25%) (adjusting pH to 5.2).

[0043] Preparation process: Substrate pretreatment: Roughening solution: 200 g / L of sulfuric acid + 50 g / L of hydrogen peroxide + 20 g / L of oxalic acid + 1 g / L of polydopamine; Roughening conditions: Temperature 45℃, time 18 minutes, dried at 60℃ after water washing.

[0044] Plasma activation: Gas ratio: 90% argon + 10% oxygen; RF power 220W, pulse frequency 10 kHz, duty cycle 30%; Treatment time 9 minutes, distance between substrate and electrode 55 mm.

[0045] Electroless nickel plating: Plating solution temperature 55℃, air stirring 250 rpm, loading amount 7 dm 2 / L; Deposition time 25 minutes, real-time monitoring of the molar ratio of complexing agent / stabilizer (2:1), dynamically replenishing sodium hypophosphite solution (1.5 mL / min).

[0046] Post-electroplating treatment: Copper plating: Copper sulfate plating solution, current density 2.5 A / dm 2 , time 15 minutes; Chrome plating: Hexavalent chromium plating solution, current density 12 A / dm 2 , for 5 minutes.

[0047] Example 2: Formulation components (per 100 L of plating solution): Nickel sulfate: 30 parts (30 kg); Sodium hypophosphite: 25 parts (25 kg, initial concentration 25 g / L, replenished to 30 g / L); Complexing agent: 3 parts of malic acid + 2 parts of succinic acid (total 5 parts, mass ratio 1.5:1); Stabilizer: Cerium nitrate nanosol (particle size 50 nm) 0.3 parts (0.3 kg); Surfactant: Sophorolipid (purity 95%) 0.05 parts (0.05 kg); pH regulator: 2 parts of ammonia water (adjust pH to 5.0).

[0048] Preparation process: Substrate pretreatment: Roughening solution: 200 g / L of sulfuric acid + 50 g / L of hydrogen peroxide (simplified formulation, without oxalic acid and polydopamine); Roughening conditions: Temperature 50°C, time 15 minutes.

[0049] Plasma activation: Gas ratio: 90% argon + 10% oxygen; RF power 200 W, pulse frequency 10 kHz, duty cycle 30%; Treatment time 10 minutes.

[0050] Electroless nickel plating: Plating solution temperature 50°C, air stirring 200 rpm; Deposition time 30 minutes, dynamically replenish sodium hypophosphite (1 mL / min).

[0051] Post-electroplating treatment: Copper plating: Current density 2 A / dm 2 , for 15 minutes; Chrome plating: Current density 10 A / dm 2 , for 5 minutes.

[0052] Example 3: Formulation components (per 100 L of plating solution): Nickel sulfate: 40 parts (40 kg); Sodium hypophosphite: 35 parts (35 kg, initial concentration 35 g / L, replenished to 40 g / L); Complexing agent: 5.7 parts of malic acid + 2.3 parts of succinic acid (total 8 parts, mass ratio 2.5:1); Stabilizer: 0.1 part (0.1 kg) of cerium nitrate nano-sol (particle size 10 nm); Surfactant: 0.1 part (0.1 kg) of sophorolipid (purity 99%); Dispersant: 0.5 part (0.5 kg) of silanized nano-silica (specific surface area 300 m² / g); pH regulator: 5 parts of ammonia water (adjust pH to 5.5).

[0053] Preparation process: Substrate pretreatment: Roughening solution: 200 g / L of sulfuric acid + 50 g / L of hydrogen peroxide + 20 g / L of oxalic acid + 1 g / L of polydopamine; Roughening conditions: temperature 40°C, time 20 minutes.

[0054] Plasma activation: Gas ratio: 90% argon + 10% oxygen; RF power 250 W, pulse frequency 10 kHz, duty cycle 30%; Treatment time 8 minutes.

[0055] Electroless nickel plating: Bath temperature 60°C, air stirring 300 rpm; Deposition time 20 minutes, dynamically add sodium hypophosphite (2 mL / min).

[0056] Post-electroplating treatment: Copper plating: current density 3 A / dm 2 , time 15 minutes; Chromium plating: current density 15 A / dm 2 , time 5 minutes.

[0057] Comparative example 1: Compared with Example 1, the difference is: remove cerium nitrate stabilizer (0 part), and the other components and process conditions are the same.

[0058] Comparative example 2: Compared with Example 1, the difference is: only use 6 parts of malic acid as the complexing agent (remove succinic acid), and the other components and process conditions are the same.

[0059] Comparative example 3: Compared with Example 1, the difference is: cancel the dynamic addition control (the initial concentration of sodium hypophosphite is fixed at 35 g / L, without real-time monitoring and addition), and the other components and process conditions are the same.

[0060] Comparative Example 4: Compared with Example 1, the difference lies in that: the plasma activation step is cancelled, and traditional sensitization (SnCl2 10 g / L, 5 minutes) and activation (PdCl2 0.1 g / L, 3 minutes) are adopted instead. The other components and process conditions are the same.

[0061] Comparative Example 5: Compared with Example 1, the difference lies in that: the plasma treatment time is shortened to 5 minutes. The other components and process conditions are the same.

[0062] Comparative Example 6: Compared with Example 1, the difference lies in that: the initial concentration of sodium hypophosphite is adjusted to 20 g / L. The other components and process conditions are the same.

[0063] Comparative Example 7: Compared with Example 1, the difference lies in that: the concentration of sophorolipid is increased to 0.2 parts. The other components and process conditions are the same.

[0064] Comparative Example 8: Compared with Example ②, the difference lies in that: hydrogen peroxide is removed from the roughening solution (only 200 g / L of sulfuric acid is retained). The other components and process conditions are the same.

[0065] Comparative Example 9: Compared with Example 3, the difference lies in that: the silanized nano-silica is replaced with unmodified nano-silica. The other components and process conditions are the same.

[0066] Experiment 1: Influence of Key Component Absence on Coating Performance Experiment Description: Purpose: To verify the necessity of cerium nitrate stabilizer, composite complexing agent, and sophorolipid concentration range Control Group: Example 1.

[0067] Experimental Group: Comparative Example 1 (removing cerium nitrate stabilizer): Compared with Example 1, cerium nitrate nano-sol (0 part) is removed, and the other conditions are the same; Comparative Example 2 (simplifying the complexing agent): Compared with Example 1, only 6 parts of malic acid are used as the complexing agent (succinic acid is removed), and the other conditions are the same; Comparative Example 7 (excessive sophorolipid): Compared with Example 1, the concentration of sophorolipid is increased to 0.2 parts, and the other conditions are the same.

[0068] Experimental Steps Preparation of Plating Solution and Substrate Treatment: Prepare the plating solutions according to the formulas of Example 1 and Comparative Examples 1 / 2 / 7 respectively; Substrate roughening (sulfuric acid / H2O2 / oxalic acid system), plasma activation (argon: oxygen = 9:1, 220W, 9 minutes).

[0069] Electroless nickel plating and post-treatment: Plating temperature is 55°C, time is 25 minutes; Copper plating (2.5A / dm 2 , 15 minutes) → Chromium plating (12A / dm 2 , 5 minutes) → Water washing and drying.

[0070] Performance testing: Coating thickness: X-ray fluorescence thickness gauge (5-point sampling, mean ± standard deviation); Adhesion: Cross-cut method (ASTM D3359 standard, grade 0 no peeling, grade 5 complete peeling); Salt spray test: Neutral salt spray chamber (5% NaCl, 35°C), record the rusting time; Wastewater COD: Potassium dichromate method (GB11914-89).

[0071] Table 1: Influence of key component adjustment on coating performance As can be seen from Table 1 above: In this experiment, by removing or adjusting the key components (cerium nitrate, complexing agent, sophorolipid), the core mechanism of action of each component in the plating solution system was revealed. The nano-size effect (10-50nm) of cerium nitrate endows it with a high specific surface area and the redox activity of surface cerium ions (Ce 3+ / Ce 4+ ), which preferentially adsorbs on the surface of active nickel nuclei in the plating solution. By inhibiting the chain decomposition reaction of sodium hypophosphite, the plating solution life is significantly extended. In Comparative Example 1, after removing cerium nitrate, the plating solution life drops sharply by 61.4% (8.3 → 3.2 MTO), and the coating thickness deviation increases sharply to 26.8%, directly verifying the irreplaceability of the stabilization mechanism of cerium nano-sol for the autocatalytic reaction balance of the plating solution.

[0072] The synergistic complexation design of malic acid and succinic acid maintains the uniform release of nickel ions through a dynamic coordination network. The α-hydroxycarboxylic acid structure of malic acid provides rapid coordination ability, while the dicarboxylic acid property of succinic acid stabilizes the pH of the plating solution through buffering, and the two form a complementary effect. In Comparative Example 2, single malic acid complexation leads to an increase in thickness deviation to 15.9%, and XRD shows that the coating grain size difference reaches ±40nm, confirming the precise regulation of the composite complexing agent on nickel deposition kinetics and avoiding problems such as missing plating or nodulation caused by local over-deposition.

[0073] Design of the critical micelle concentration (CMC) of sophorolipid (0.05 - 0.1 parts) reduces the surface tension of the plating solution through directional adsorption and improves the wettability of the substrate. Excessive sophorolipid (Comparative Example 7) reduces the surface tension below 25 mN / m, causing pinhole defects in the coating (pinhole rate 7%). At the same time, the excessive sugar lipid molecules aggregate due to the hydrophobic chains, resulting in more foam and increasing the process complexity. This phenomenon is consistent with the micelle formation mechanism of sophorolipid: after exceeding the CMC, the molecules change from monolayer adsorption to the micelle state and lose the ability to directionally wet the microporous structure.

[0074] In summary, Experiment 1 verified the inseparability of component synergy and process parameter design from three aspects: redox inhibition, complexation equilibrium, and interfacial wetting, through systematic comparison of component deletion and parameter out-of-range, providing direct experimental support for the inventiveness of the invention.

[0075] Experiment 2: Influence of Process Condition Adjustment on Coating Performance Experiment Description Purpose: To verify the necessity of plasma activation, dynamic replenishment control, and plasma treatment time.

[0076] Control Group: Example 1 (standard process conditions).

[0077] Experimental Group: Comparative Example 3 (canceling dynamic replenishment): Compared with Example 1, the initial concentration of sodium hypophosphite was fixed at 35 g / L, without real-time monitoring and replenishment; Comparative Example 4 (traditional sensitization / activation): Compared with Example 1, plasma activation was canceled, and SnCl2 (10 g / L, 5 minutes) + PdCl2 (0.1 g / L, 3 minutes) activation was used instead; Comparative Example 5 (insufficient plasma time): Compared with Example 1, the plasma treatment time was shortened to 5 minutes.

[0078] Experimental Steps: Substrate Treatment: Control Group: Roughening and plasma activation were carried out according to Example 1 (argon: oxygen = 9:1, 220 W, 9 minutes); Comparative Examples 3 / 4 / 5: The corresponding process parameters were adjusted respectively, and the remaining pretreatment steps were the same as those of the control group.

[0079] Electroless Nickel Plating and Post-treatment: The plating temperature was 55 °C and the time was 25 minutes; Dynamic replenishment was canceled in Comparative Example 3, and the initial concentration of sodium hypophosphite was fixed at 35 g / L; The parameters of the post-electroplating treatment (copper plating → chromium plating) were the same as those of the control group.

[0080] Performance Testing: Adhesion: Cross - cut method (ASTM D3359 standard); Bath life: Measured by the number of metal turnovers (MTO); Wastewater COD: Potassium dichromate method (GB11914 - 89); Process duration: The total time from roughening to chromium plating.

[0081] Table 2: Influence of process condition adjustment on coating properties As can be seen from Table 2 above: The essence of dynamic replenishment control is to maintain the balance between the reduction efficiency of sodium hypophosphite and the deposition rate of nickel ions by real - time monitoring of the molar ratio of complexing agent to stabilizer (2:1 ± 10%). Sodium hypophosphite is both a reducing agent and a pH buffer in the plating bath, and its concentration gradient directly affects the formation and growth kinetics of nickel crystal nuclei. After canceling the dynamic replenishment in Comparative Example 3, although the initial concentration of sodium hypophosphite was 35 g / L, it gradually decreased below the critical value (25 g / L) with the reaction consumption, resulting in a pH fluctuation of ±1.2 in the plating bath. The reduction path of nickel ions changed from uniform nucleation to disordered aggregation. XRD showed that the grain size distribution of the coating in the non - replenished group broadened (±35 nm), and the surface nickel oxide content increased by 12%, which was directly related to the local oxidation reaction caused by insufficient sodium hypophosphite. The dynamic replenishment strategy controlled the concentration deviation within ±5% by precise liquid addition (1.5 mL / min), increasing the bath life from 4.1 MTO to 8.4 MTO, verifying the decisive role of this design in the self - stabilizing mechanism of the plating bath.

[0082] The core advantage of plasma activation replacing traditional Sn / Pd activation is to achieve surface roughening and construction of chemical active sites in one step. Argon ion bombardment (radio - frequency power 220 W) forms micron - scale pits (Ra≈0.5μm) on the substrate surface through physical sputtering, while oxygen radicals (10% O2) oxidize to generate carboxyl groups (—COOH), providing high - density polar anchor points for nickel deposition. In Comparative Example 4, when using Sn / Pd activation, the size distribution of palladium particles was uneven (50 - 200 nm), resulting in preferential deposition of the nickel layer at the edges of the micro - pits, forming stress concentration points. After the cross - cut test, the coating peeled off in pieces (adhesion level 2). In the plasma activation group, nickel grains spread evenly along the pits (SEM showed a coverage rate > 95%), and the adhesion reached level 0. In addition, the Sn 2+ / Pd 2+ wastewater COD of the traditional process was as high as 352 mg / L, highlighting the breakthrough of plasma activation in environmental protection in reverse - its wastewater COD was only 119 mg / L and there was no heavy metal residue.

[0083] The setting of the plasma treatment time (8 - 10 minutes) is essentially a function of the energy input and the surface modification depth. When the treatment time is insufficient (Comparative Example 5, 5 minutes), the cumulative bombardment energy of argon ions is insufficient, the surface roughness Ra is only 0.2 μm (target value 0.5 μm), and the coverage rate of polar groups is < 45%. The low-roughness surface reduces the mechanical interlocking effect of the nickel layer, while the insufficient polar groups weaken the chemical adsorption force, jointly resulting in the bonding force dropping to level 1 (edge peeling). XPS analysis shows that the density of —COOH in the short-time treatment group is 3.2 atoms / nm 2 , while that in the control group reaches 7.8 atoms / nm 2 , directly restricting the uniform distribution of nickel crystal nuclei. At the same time, the insufficient energy input deteriorates the wettability of the substrate (contact angle 65° vs 22° in the control group), the plating solution does not penetrate sufficiently in the micropores, and the thickness at the top of the thread is only 1.1 μm (design requirement ≥ 1.5 μm). The optimization of the time parameter is essentially to balance the surface activation energy efficiency and the process economy, ensuring the best match between the coating performance and the energy consumption cost.

[0084] This summary deconstructs the relationship between process conditions and coating performance into a quantifiable mechanism model from three perspectives: the chemical equilibrium of the plating solution, the surface physicochemical modification, and the energy input threshold. The data deviation (such as bonding force level 1 - 2, COD 119 - 352 mg / L) objectively reflects the sensitivity of parameter fluctuations to the final effect.

[0085] Experiment 3: Influence of parameters beyond the range on coating performance Experiment description Purpose: To verify the necessity of the concentration range of sodium hypophosphite, plasma treatment time, and sophorolipid concentration.

[0086] Control group: Example 1 (standard formulation and process parameters).

[0087] Experimental groups: Comparative Example 5 (insufficient plasma time): Compared with Example 1, the plasma treatment time was shortened to 5 minutes; Comparative Example 6 (too low concentration of sodium hypophosphite): Compared with Example 1, the initial concentration of sodium hypophosphite was adjusted to 20 g / L; Comparative Example 7 (excessive sophorolipid): Compared with Example 1, the concentration of sophorolipid was increased to 0.2 parts.

[0088] Experimental procedures Preparation of plating solution and substrate treatment: Control group: Conducted according to the formulation and process parameters of Example 1; Comparative Examples 5 / 6 / 7: Respective parameters (plasma time, concentration of sodium hypophosphite, amount of sophorolipid) were adjusted, and the other conditions were the same as those in the control group.

[0089] Electroless nickel plating and post-treatment: The plating temperature is 55 °C and the time is 25 minutes; In Comparative Example, the concentration of sodium hypophosphite is fixed at 20 g / L without dynamic replenishment; The parameters of the post-electroplating treatment (copper plating → chromium plating) are the same as those of the control group.

[0090] Performance testing: Coating thickness: X-ray fluorescence thickness gauge (5-point sampling, mean ± standard deviation); Surface roughness: white light interferometer (Ra value, mean of three measurements); Adhesion: cross-cut method (ASTM D3359 standard, grade 0 is the best); Wastewater COD: potassium dichromate method (GB11914-89).

[0091] Table 3: Influence of out-of-range parameters on coating performance As can be seen from Table 3 above: The concentration range of sodium hypophosphite (25 - 35 g / L) maintains the stable reduction potential of nickel ions through a dynamic replenishment strategy. Its essence is to balance the consumption rate of sodium hypophosphite and the electron transfer demand for nickel deposition. Sodium hypophosphite acts as both a reducing agent (providing electrons) and a pH buffer (H2PO2 - / HPO3 2- system) in the plating solution. When the concentration is below the critical value (25 g / L), the reduction potential drops suddenly from -0.45 V (vs. SHE) to -0.32 V, resulting in insufficient reduction driving force for nickel ions (Ni 2+ ). In Comparative Example 6, when the concentration of sodium hypophosphite drops to 20 g / L, the coating thickness is only 0.49 μm (1.53 μm in the control group), and the surface dendritic structure (observed by SEM) verifies the disordered growth caused by local electron enrichment at low concentrations. This phenomenon is consistent with the non-linear relationship between the concentration of sodium hypophosphite and the reduction efficiency: when the concentration is below 25 g / L, the decomposition rate of sodium hypophosphite (k = 0.12 min -1 ) exceeds the replenishment control ability, and the plating solution life drops from 8.3 MTO to 4.2 MTO.

[0092] The setting of the plasma treatment time (8 - 10 minutes) is directly related to the surface activation energy threshold. Argon ion bombardment (energy density ≥ 5 J / cm 2)(A micron-scale rough surface (Ra≈0.5μm) is formed by physical sputtering, and the continuous oxidation of oxygen radicals (>7 minutes) constructs a polar group network of carboxyl (-COOH) and hydroxyl (-OH) on the substrate surface. The coverage rate needs to be ≥85% to ensure the uniform anchoring of nickel crystal nuclei. When the treatment time in Comparative Example 5 is shortened to 5 minutes, the coverage rate of polar groups is only 42% (XPS quantification), and the surface roughness Ra drops to 0.2μm, resulting in a decrease in the coating adhesion to Grade 1 (edge peeling after cross-cutting). This time-energy cumulative effect indicates that short-term treatment cannot break through the chemical inert barrier (such as hydrocarbon pollutants) on the substrate surface to ensure the balance between activation energy efficiency and process cost.)

[0093] )(The upper limit of the sophorolipid concentration (0.1 part) is set based on its critical micelle concentration (CMC≈0.08 part). When below the CMC, sophorolipid molecules adsorb in a monolayer to reduce the surface tension of the plating solution ( =45→32mN / m), improving wettability; after exceeding the CMC, the molecules self-assemble into micelles (diameter 50-100nm), and the hydrophobic core adsorbs nickel ions, leading to abnormal local deposition rates. When the sophorolipid concentration in Comparative Example 7 is increased to 0.2 part (2.5 times higher than the CMC), the pinhole rate of the coating increases to 9%, and the wastewater COD increases to 137mg / L (119mg / L for the control group). The shielding effect of micelles results in uneven microscopic wetting of the plating solution (contact angle fluctuation ±8°), and the aggregation of hydrophobic chains further interferes with the diffusion path of nickel ions (Fick's law deviation ±22%). The scientific limitation of the concentration range ensures that sophorolipid functions in a single molecular state to achieve directional wetting while avoiding the accumulation of degradation by-products.)

[0094] Experiment 4: Comparison of roughening process optimization Experiment description )(Purpose: To verify the synergistic effect of hydrogen peroxide in the roughening solution on the micro-etching of the substrate surface.)

[0095] )(Control group: Example 2 (standard roughening process: sulfuric acid / H2O2 / oxalic acid = 10:3:2, volume ratio).)

[0096] )(Experimental group: Comparative Example 8 (removing H2O2): The roughening solution only contains sulfuric acid / oxalic acid = 10:2, and the other process parameters are the same as those in Example 2.)

[0097] Experimental steps )(Roughening treatment:) )(Control group: The substrate is immersed in a mixed solution of sulfuric acid (30%), H2O2 (5%), and oxalic acid (8%) (50°C, 8 minutes).) )(Comparative Example 8: The substrate is immersed in a mixed solution of sulfuric acid (30%) and oxalic acid (8%) (50°C, 8 minutes).)

[0098] )(Subsequent process:) Plasma activation (argon: oxygen = 9:1, 220 W, 9 minutes) → electroless nickel plating (formulation of Example 2) → copper plating → chromium plating.

[0099] Performance testing: Roughening rate: weight loss method (mg / cm 2 min); Surface morphology: observing the density and depth of micro-etching pits by SEM; Adhesion: cross-cut method (ASTM D3359); Heavy metal content in wastewater: detecting the Sn / Pb residues by ICP-MS.

[0100] Table 4: Influence of roughening process adjustment on coating properties As can be seen from Table 4 above: The core role of H2O2 in the roughening solution is to generate active hydroxyl radicals (OH) through the Fenton reaction (Fe 2+ / H2O2 system). Its oxidation potential (2.8 V) is much higher than that of single acid etching (sulfuric acid / oxalic acid system ≤ 1.5 V), and it can efficiently decompose the hydrocarbon pollutants on the substrate surface and initiate micro-area selective etching. After removing H2O2 in Comparative Example 8, the roughening rate decreased from 0.38 mg / cm 2 min to 0.21 mg / cm 2 min. SEM showed that the density of micro-etching pits decreased by 46% (6.7 vs 12.3 pits / μm 2 ). This phenomenon is directly related to the directional oxidation mechanism of OH - the absence of H2O2 leads to the etching process relying only on protonation (H + attack), which cannot penetrate the surface passivation layer (such as alumina film), weakening the mechanical biting effect on the substrate surface and reducing the adhesion from grade 0 to grade 2. At the same time, insufficient roughening forced the process time to be extended to 12 minutes (8 minutes for the control group), exacerbating the dissolution of the lead salt stabilizer (lead nitrate), and increasing the Pb 2+ residue in the wastewater to 82 ppb (control group < 5 ppb), which reversely verifies the dual necessity of H2O2 in improving etching efficiency and reducing heavy metal pollution.

[0101] The synergistic effect of the roughening solution components is reflected in the oxidation-protonation coupling mechanism of H2O2 and sulfuric acid. Sulfuric acid provides a high concentration of H +It promotes the dissolution of metal oxides, and H2O2 continuously generates oxidation active substances through a chain reaction (OH→HOO→O2). The two work together to form deep and uniform micro-etching pits (average depth 0.8 μm). When only sulfuric acid / oxalic acid is used in Comparative Example 8, the randomness of the etching direction increases, and the depth distribution of the micro-etching pits is discrete (0.2 - 1.5 μm, standard deviation ±0.4 μm), resulting in non-plating at complex structures such as the root of the thread of the coating (thickness only 0.8 μm). XPS analysis further shows that the absence of H2O2 increases the carbon residue on the substrate surface by 18% (the peak area ratio of C1s is 32% vs 14% in the control group), and the coverage rate of polar groups (—COOH) is less than 35%, significantly reducing the wettability of the plating solution (the contact angle increases from 22° to 47°). This chemical-topographical linkage deterioration confirms the irreplaceability of H2O2 in the roughening formulation.

[0102] The balance between process economy and environmental protection is achieved through the introduction of H2O2. The high oxidation ability of H2O2 compresses the roughening time to 8 minutes (Comparative Example 8 requires 12 minutes to achieve the same etching amount), reducing the energy consumption cost by about 40%. At the same time, its completely decomposed products (H2O, O2) have no secondary pollution, while the lead salt dissolution caused by traditional extended etching (Pb in the wastewater of Comparative Example 8 2+ 82 ppb) requires additional wastewater treatment costs. The concentration of H2O2 (3 - 5%) is locked through experiments, which can not only avoid over-etching (when >5%, the micro-crack rate increases by 12%), but also inhibit side reactions (such as H2O2 self-decomposition to generate gas). Data deviations (such as roughening rate 0.21 - 0.38, Pb 2+ residue <5 - 82 ppb) objectively quantify the cascading effects of component absence on performance and cost.

[0103] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A highly dispersed plastic bathroom electroplating electroless nickel solution, characterized in that, Comprising the following components in parts by mass: Nickel sulfate: 30 - 40 parts; Sodium hypophosphite: 25 - 35 parts; Complexing agent: 5 - 8 parts, composed of malic acid and succinic acid; Stabilizer: 0.1 - 0.3 part; Surfactant: 0.05 - 0.1 part; pH regulator: 1 - 5 parts.

2. The electroless nickel plating bath for plastic sanitary ware with high dispersibility according to claim 1, characterized in that, The complexing agent is composed of malic acid and succinic acid, and the mass ratio of the two is (1.5 - 2.5):

1.

3. A highly dispersive electroplating electroless nickel solution for plastic sanitary ware according to claim 1, characterized in that, The stabilizer is cerium nitrate, the particle size of the cerium nitrate is 10 - 50 nm, and it is dispersed in the plating solution in the form of a nano - sol.

4. A high-dispersion plastic bathroom electroplating electroless nickel plating solution according to claim 1, characterized in that, The surfactant is sophorolipid, its purity is 95% - 99%, and the addition amount is 0.05 - 0.1 part. The critical micelle concentration of the sophorolipid is 0.05 - 0.1 part.

5. A highly dispersible electroplating electroless nickel solution for plastic sanitary ware according to claim 1, characterized in that, The electroless nickel plating solution further contains a dispersant: Dispersant: Nano-silica modified with silane coupling agent, the specific surface area of the nano-silica is 200 - 300 m 2 / g, and the pore size is 2 - 5 nm.

6. A preparation process of a highly dispersive electroless nickel plating solution for plastic sanitary ware, according to any one of claims 1-5, a highly dispersive electroless nickel plating solution for plastic sanitary ware, characterized in that, Including the following steps: Step 1, substrate pretreatment: The plastic substrate is surface - roughened with an acidic roughening solution; Step 2, plasma activation: The roughened substrate is subjected to plasma treatment in a mixed gas containing oxygen; Step 3, electroless nickel plating: The activated substrate is immersed in the electroless nickel plating solution, maintaining the plating solution temperature at 50 - 60 °C, and the reducing agent and stabilizer are monitored and replenished in real time during the plating process; Step 4, post - electroplating treatment: The nickel - plated substrate is subjected to copper plating and chromium plating treatments.

7. The preparation process of a highly dispersive plastic bathroom electroplated electroless nickel solution according to claim 6, characterized in that, The specific operation of Step 1 includes: The plastic substrate is immersed in an environmentally friendly roughening solution, which is composed of sulfuric acid, hydrogen peroxide, oxalic acid and polydopamine. The roughening temperature is 40 - 50 °C, and the time is 15 - 20 minutes; After roughening, wash with water and dry.

8. The preparation process of a highly dispersive plastic sanitary ware electroplating electroless nickel solution according to claim 6, characterized in that, The specific operation of Step 2 includes: The roughened substrate is placed in a pulsed radio - frequency glow discharge device, and a mixed gas of argon and oxygen with a volume ratio of 9:1 is introduced; Set the radio - frequency power to 200 - 250 W, the pulse frequency to 10 kHz, the duty cycle to 30%, and the treatment time to 8 - 10 minutes; After treatment, directly perform electroless nickel plating without sensitization or activation in separate steps.

9. The preparation process of a highly dispersed plastic sanitary ware electroplated electroless nickel solution according to claim 6, characterized in that, The specific operation of Step 3 includes: During electroless nickel plating, the molar ratio of the complexing agent to the stabilizer is monitored in real time through an on - line conductivity sensor, and the ratio is maintained at 2:1 ± 10%; When the molar ratio deviates, the sodium hypophosphite solution is replenished at a rate of 1 - 2 mL / min.

10. The preparation process of a highly dispersive plastic sanitary ware electroplating electroless nickel solution according to claim 6, characterized in that, The specific operation of Step 4 includes: Copper plating treatment: current density 2 - 3 A / dm 2 , time 15 minutes, the plating solution is a copper sulfate system; Chrome plating treatment: current density 10 - 15 A / dm 2 , time 5 minutes, plating solution is a hexavalent chromium system; After plating, wash with water and dry.

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