A low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, its preparation method, and its application.

Abstract

This invention relates to the field of metal surface treatment technology, and discloses a low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, its preparation method, and its application. It aims to solve the technical problem of balancing environmental friendliness and performance in existing cyanide zinc plating processes, which are limited by traditional strong alkaline systems. The composite plating solution, per liter, contains 15-30 g / L of a low-cyanide complexing agent (composed of sodium cyanide and potassium cyanide in a specific mass ratio), 40-80 g / L of a ternary cyanide-free auxiliary complexing agent, 20-50 g / L of zinc chloride main salt, 5-15 g / L of nano-wear-resistant reinforcing particles, 3-10 g / L of corrosion-resistant alloy components, 1-5 g / L of surfactant additives, and the balance being deionized water. The pH value of the plating solution is strictly controlled between 4.0 and 6.0. The preparation method includes four steps: preparation of the base solution, introduction of the main salt and corrosion-resistant alloy components, high-speed stirring and ultrasonic dispersion of nanoparticles, pH adjustment, and cooling filtration. Specific electroplating process conditions are used during application. This invention breaks through the traditional technical prejudice that cyanide electroplating must use a strong alkaline system, controlling the total cyanide concentration to within 30g / L, achieving a synergistic improvement in environmental protection and functionality. The coating can withstand neutral salt spray for 120-150 hours, Taber abrasion is reduced by more than 30% compared with traditional processes, the hardness reaches HV 500-600, and the plating solution has excellent stability. It can be widely used in the electroplating treatment of various metal products, and has outstanding advantages in safety, environmental protection and high performance.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to a composite zinc plating solution with low cyanide content and excellent corrosion resistance and wear resistance, as well as its preparation method and application. Background Technology

[0002] Cyanide zinc plating, due to its good solution stability, fine coating crystals, and strong adhesion, was once the mainstream technology for corrosion protection of steel parts. However, traditional processes involve high cyanide concentrations (>50g / L), which are highly toxic and cause severe pollution, posing a serious environmental challenge. The industry has shifted towards developing low-cyanide / cyanide-free zinc plating technologies, but generally faces the dilemma of balancing environmental protection and performance. Lowering the cyanide concentration leads to performance degradation: Simply reducing the cyanide content reduces the complexing ability and stability of the plating solution, and the corrosion resistance of the coating (usually NSS < 72h) is far inferior to that of high-cyanide coatings.

[0003] Functional modification is difficult to achieve in low-cyanide systems: nano-wear-resistant particles (such as SiC) and corrosion-resistant alloying elements (such as Ni and Co) added to improve performance are prone to agglomeration or uncontrolled co-deposition in low-cyanide weak complexation systems, which in turn damages the coating quality.

[0004] More importantly, for safety reasons, cyanide plating must be carried out in a strongly alkaline environment (pH>10) to suppress the generation of highly toxic hydrogen cyanide (HCN) gas. This has created a profound technical bias that "cyanide zinc plating must use a strongly alkaline system," and has also limited the possibility of optimizing the electrochemical process by adjusting the pH value or introducing components that are more stable under acidic conditions (such as certain alloy salts).

[0005] Therefore, developing an electroplating solution that can overcome the limitations of strong alkali processes and achieve both stability of the plating solution and improved corrosion resistance and wear resistance of the coating at a safe and controllable low cyanide concentration (≤30g / L) is a technical problem that the field has long desired to solve but has not yet been able to overcome. Summary of the Invention

[0006] This invention aims to overcome the biases and defects of existing technologies and provide a low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, its preparation method, and its application. The core objective of this invention is to achieve stable co-deposition of nano-wear-resistant particles and corrosion-resistant alloying elements within a stable system by designing an innovative "weakly acidic low-cyanide complexing system," ensuring operational safety. This results in a composite plating layer with comprehensive performance surpassing that of traditional high-cyanide plating layers.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, characterized in that it comprises the following components at the following concentrations per liter of plating solution: Low-cyanide complexing agent 15-30 g / L; Cyanide-free auxiliary complexing agent 40-80 g / L; Main salt 20-50 g / L; Wear-resistant reinforcing particles: 5-15 g / L; Corrosion-resistant alloy composition 3-10 g / L; Surfactant additive 1-5 g / L; The remainder is deionized water; The pH value of the composite plating solution is 4.0-6.0; The low-cyanide complexing agent is a mixture of sodium cyanide and potassium cyanide in a mass ratio of 1:(1-2); The cyanide-free auxiliary complexing agent is composed of sodium citrate, potassium sodium tartrate and triethanolamine in a mass ratio of 3:2:1; The wear-resistant reinforcing particles are a mixture of nano-silicon carbide particles with a particle size of 50-100 nm and nano-alumina particles in a mass ratio of 2:1. The corrosion-resistant alloy component is a mixture of nickel sulfate and cobalt sulfate in a mass ratio of 3:1; The surfactant additive is composed of a brightener, a leveling agent and a dispersant mixed in a mass ratio of 2:2:1, wherein the brightener is 1,4-butynediol, the leveling agent is sodium allyl sulfonate and the dispersant is sodium dodecyl sulfate. The main salt is zinc chloride.

[0008] Safety and stability mechanism: The plating solution of this invention can operate safely and stably under weakly acidic conditions of pH 4.0-6.0. The key lies in: (1) The significant reduction in total cyanide concentration (≤30g / L) reduces the potential risk of free CN⁻ at the source; (2) A specific ternary cyanide-free auxiliary complexing agent (sodium citrate-sodium potassium tartrate-triethanolamine) constitutes a strong buffer system, which can effectively stabilize the pH value and preferentially complex with some zinc, nickel and cobalt ions, reducing the interference of free metal ions on the stability of cyanide complex ions. (3) Under the specified ratio and concentration, cyanide ions mainly exist in the form of stable zinc cyanide and nickel cyanide complex ions. Under operating temperatures of 50-60℃ and good ventilation conditions, the HCN gas concentration above the plating bath was found to be far below the national safety standard limit. This "weakly acidic low-cyanide complex system" is the common basis for achieving both safety and functionality in this invention.

[0009] A method for preparing the low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, characterized by comprising the following steps: S1. Preparation of base solution: Under stirring conditions of 40-50℃ and 200-300 r / min, add the formulated amount of low-cyanide complexing agent and cyanide-free auxiliary complexing agent to deionized water in sequence, and stir until completely dissolved to obtain a homogeneous base complexing solution; S2. Introduction of main salt and alloy components: Add the prescribed amount of zinc chloride to the basic complex solution obtained in step S1, stir to dissolve, then add the prescribed amount of corrosion-resistant alloy components, and stir until completely dissolved; S3. Nanoparticle dispersion: Add the prescribed amount of wear-resistant reinforcing particles to the solution obtained in step S2, increase the stirring speed to 400-500 r / min, and simultaneously perform ultrasonic dispersion treatment at a frequency of 20-30 kHz for 10-15 min. S4. Post-treatment: Add the formulated amount of surfactant additive to the dispersion obtained in step S3, stir to dissolve, adjust the pH value to 4.0-6.0 with acid or alkali solution, cool and filter to obtain the composite plating solution.

[0010] The application of the aforementioned low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution in the electroplating of metal products is characterized by the following electroplating process conditions: plating solution temperature 50-60℃, cathode current density 2.0-3.0 A / dm², electroplating time 30-60 min, and the plating solution being stirred.

[0011] Compared with the prior art, the present invention has the following significant advantages: 1. Breakthrough in safety and environmental protection: A "low-cyanide complexation system" that can operate stably under weakly acidic conditions of pH 4.0-6.0 has been successfully constructed, with a total cyanide concentration of ≤30g / L. Under the premise of ensuring production safety, this breaks the traditional limitation that cyanide electroplating must use a strong alkaline system, and significantly reduces pollution at the source.

[0012] Synergistic leap in coating performance: Corrosion resistance: The weakly acidic environment is conducive to the co-deposition of Ni²⁺ and Co²⁺, forming a dense Zn-Ni-Co alloy phase with Zn, which makes the coating resistant to neutral salt spray for 120-150 hours.

[0013] Wear resistance: The specific ternary complexing agent and pH environment ensure the uniform dispersion and co-deposition of nano-SiC and Al2O3 particles, forming a composite reinforcing phase. The Taber wear is reduced by more than 30% compared with the traditional process, and the hardness reaches HV 500-600.

[0014] Excellent plating solution stability: The ternary cyanide-free auxiliary complexing agent has multiple functions of complexing, buffering, and dispersion stabilization. The plating solution has good stability in the weakly acidic range and can be used continuously for more than 35 days.

[0015] The inventive concept is not obvious: combining "significantly reducing cyanide concentration", "adjusting the working pH to weakly acidic", "introducing a specific ternary cyanide-free auxiliary complexing agent" and "selecting zinc chloride as the main salt" is a systematic innovative solution that solves multiple technical pain points and produces unexpected technical effects. It is not a simple combination of existing technologies. Attached Figure Description

[0016] Figure 1 This is a flow chart of the preparation process of the composite plating solution of the present invention.

[0017] The process is as follows: Deionized water (heated and stirred) → + low-cyanide and cyanide-free auxiliary complexing agent (dissolved) → + zinc chloride (dissolved) → + corrosion-resistant alloy component (dissolved) → + wear-resistant reinforcing particles (high-speed stirring + ultrasonic dispersion) → + surfactant additive (dissolved) → pH adjustment → cooling and filtration → finished product. Detailed Implementation

[0018] The present invention is further illustrated below through examples and comparative examples. All raw materials are commercially available industrial grade.

[0019] Examples 1-3 According to the formula in Table 1, the plating solution was prepared according to the aforementioned method: sodium cyanide / potassium, sodium citrate / potassium sodium tartrate / triethanolamine were dissolved sequentially under stirring at 45℃ and 250r / min; after adding zinc chloride to dissolve, nickel sulfate / cobalt sulfate was added; nano SiC / Al2O3 was added, the speed was increased to 450r / min and ultrasonic treatment (25kHz, 120W) was performed for 12min; 1,4-butynediol / sodium allyl sulfonate / sodium dodecyl sulfate was added; the pH was adjusted with NaOH, and the solution was cooled and filtered.

[0020] Comparative Example 1 (Traditional high-cyanide alkaline zinc plating) Sodium cyanide 60g / L, sodium hydroxide 120g / L, zinc oxide 10g / L, conventional process.

[0021] Comparative Example 2 (lacking synergistic components) Total cyanide 30g / L (sodium cyanide only), no ternary cyanide auxiliary complexing agent, 10g / L nano SiC added (no Al2O3), no nickel cobalt salt, zinc oxide as the main salt, pH>10, prepared according to conventional alkaline cyanide process.

[0022] Using the exact same components and concentrations as in Example 2, but adjusting the pH of the plating solution to 10.5 with sodium hydroxide, the performance of this formulation system under alkaline conditions was examined.

[0023] The coating obtained by the above plating solution was tested, and the results are shown in Table 1.

[0024] Table 1: Performance Comparison Results analysis: The invention is remarkably effective: Examples 1-3, under low cyanide and weak acid conditions, outperformed Comparative Example 1, which was under high cyanide and alkaline conditions, demonstrating the breakthrough nature of the solution.

[0025] Synergy is indispensable: Comparative Example 2 lacks key components, resulting in a comprehensive deterioration in performance, proving that the component compounding of the present invention is a necessary synergistic system.

[0026] A weakly acidic pH is a critical condition: the results of Comparative Example 3 show that even when using all the components of this invention, simply adjusting the pH to the traditional alkaline range (pH 10.5) significantly reduces the overall performance of the coating and the stability of the plating solution, failing to achieve the effects of this invention within the pH range of 4.0-6.0. This demonstrates that the aforementioned weakly acidic environment is an essential process condition for achieving stable dispersion of nanoparticles, alloy co-deposition, and ultimately obtaining a highly corrosion-resistant and wear-resistant coating in this invention.

Claims

1. A low-cyanide, high-corrosion-resistant, and high-wear-resistant composite plating solution, characterized in that, The plating solution consists of the following components at the following concentrations per liter: Low-cyanide complexing agent 15-30 g / L; Cyanide-free auxiliary complexing agent 40-80 g / L; Main salt 20-50 g / L; Wear-resistant reinforcing particles: 5-15 g / L; Corrosion-resistant alloy composition 3-10 g / L; Surfactant additive 1-5 g / L; The remainder is deionized water; The pH value of the composite plating solution is 4.0-6.0; The low-cyanide complexing agent is a mixture of sodium cyanide and potassium cyanide in a mass ratio of 1:(1-2); The cyanide-free auxiliary complexing agent is composed of sodium citrate, potassium sodium tartrate and triethanolamine in a mass ratio of 3:2:1; The wear-resistant reinforcing particles are a mixture of nano-silicon carbide particles with a particle size of 50-100 nm and nano-alumina particles in a mass ratio of 2:

1. The corrosion-resistant alloy component is a mixture of nickel sulfate and cobalt sulfate in a mass ratio of 3:1; The surfactant additive is composed of a brightener, a leveling agent and a dispersant mixed in a mass ratio of 2:2:1, wherein the brightener is 1,4-butynediol, the leveling agent is sodium allyl sulfonate and the dispersant is sodium dodecyl sulfate. The main salt is zinc chloride.

2. The composite plating solution according to claim 1, wherein Based on per liter of plating solution: the concentration of the low-cyanide complexing agent is 20-25 g / L; the concentration of the cyanide-free auxiliary complexing agent is 50-70 g / L; the concentration of the wear-resistant reinforcing particles is 8-12 g / L; the concentration of the corrosion-resistant alloy component is 5-8 g / L; and the concentration of the surface-active additive is 2-4 g / L.

3. The composite plating solution according to claim 1 or 2, characterized by The particle size of the nano-silicon carbide particles and nano-alumina particles is 60-80 nm.

4. A method for preparing the low-cyanide high-corrosion-resistance high-wear-resistance composite plating solution according to any one of claims 1 to 3, characterized by, Includes the following steps: S1. Preparation of base solution: Under stirring conditions of 40-50℃ and 200-300 r / min, add the formulated amount of low-cyanide complexing agent and cyanide-free auxiliary complexing agent to deionized water in sequence, and stir until completely dissolved to obtain the base complexing solution; S2. Introduction of main salt and alloy components: Add the prescribed amount of zinc chloride to the basic complex solution obtained in step S1, stir to dissolve, then add the prescribed amount of corrosion-resistant alloy components, and stir until completely dissolved; S3. Nanoparticle dispersion: Add the prescribed amount of wear-resistant reinforcing particles to the solution obtained in step S2, increase the stirring speed to 400-500 r / min, and simultaneously perform ultrasonic dispersion treatment at a frequency of 20-30 kHz for 10-15 min. S4. Post-treatment: Add the prescribed amount of surfactant to the dispersion obtained in step S3, stir to dissolve, adjust the pH value to 4.0-6.0 with acid or alkali solution, cool and filter to obtain the final product.

5. The use of the low-cyanide high-corrosion-resistance high-wear-resistance composite plating solution according to any one of claims 1 to 3 for electroplating a metal product, characterized in that, The electroplating process conditions are as follows: plating solution temperature 50-60℃, cathode current density 2.0-3.0 A / dm², electroplating time 30-60 min, and the plating solution is in a stirring state.

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