Anti-corrosion composite coating for silver-copper alloy precision component and preparation method of anti-corrosion composite coating

Abstract

The invention relates to the technical field of silver-copper alloy surface protection, in particular to a silver-copper alloy precision component anti-corrosion composite coating and a preparation method thereof. The anti-corrosion composite coating comprises a silver-loaded antibacterial layer and a cosmetic corrosion prevention layer. The coating provided by the invention adopts a three-layer composite structure of the chemical pretreatment layer, the silver-loaded antibacterial layer and the cosmetic corrosion prevention layer, has excellent cosmetic corrosion prevention and antibacterial properties, can keep gloss and has strong binding force.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silver-copper alloy surface protection, and in particular to a silver-copper alloy precision component corrosion-resistant composite coating and a preparation method thereof. BACKGROUND

[0002] Silver-copper alloy combines the excellent metallic luster of silver and the good mechanical properties of copper, and is widely used in the field of precision components due to its unique decoration and practicality, including precision components, high-frequency contact decorative components, and close-to-body functional components, which are one of the core substrates of high-end personal products. However, during long-term use, silver-copper alloy components face multiple problems: on the one hand, they are prone to contact with cosmetics such as perfume, foundation, and skin care products, which contain sulfides, acid and alkali components that can cause chemical corrosion on the surface of silver-copper alloy, resulting in corrosion spots, blackening and loss of luster, and serious damage to the appearance integrity; on the other hand, in the context of close-to-body high-frequency contact, the surface of the component is prone to the growth of common pathogenic bacteria such as Escherichia coli and Staphylococcus aureus, posing a significant health and safety hazard.

[0003] To solve the above problems of silver-copper alloy components, existing technologies have developed some surface treatment solutions, but there are still obvious limitations:

[0004] (1) Single-function protective coating technology

[0005] CN101160146B discloses a silver composition containing silver sulfate and a coating method, which achieves certain antibacterial or local protection effect by coating a silver-containing composition on the surface of the substrate, but only designs for a single corrosion factor, does not target the synergistic corrosion mechanism of sulfides, acid and alkali components in cosmetics, has poor resistance to such components, and is still prone to corrosion spots and loss of luster after long-term contact; at the same time, its antibacterial function is single and lacks long-term design, which cannot effectively solve the problem of bacterial growth in close-to-body scenarios.

[0006] (2) Traditional physical covering coating technology

[0007] Ordinary painting and resin covering achieve protection by physical shielding, but the interfacial adhesion between the coating and the silver-copper alloy substrate is insufficient, and the coating is prone to peeling and falling off under the action of friction and scratching during carrying, resulting in loss of protection; in addition, some coating materials have poor transparency or mismatched refractive index, which can cover the original metallic luster of silver-copper alloy, seriously reducing its decorative properties, and cannot meet the use requirements of decorative components.

[0008] In summary, the current silver-copper alloy precision component surface protection technology still cannot meet the comprehensive performance requirements of "anti-cosmetic corrosion, antibacterial, gloss retention, and friction resistance" in the on-body use scenario, and a new technology is urgently needed to solve the shortcomings of existing solutions. SUMMARY

[0009] The present application provides a silver-copper alloy precision component anti-corrosion composite coating and a preparation method thereof. The coating of the present application adopts a three-layer composite structure of "chemical pretreatment layer + silver-loaded antibacterial layer + anti-cosmetic corrosion layer", has excellent anti-cosmetic corrosion and antibacterial performance, and can also retain gloss and have strong adhesion.

[0010] In a first aspect, the present application provides a silver-copper alloy precision component anti-corrosion composite coating, which adopts the following technical solution:

[0011] A silver-copper alloy precision component anti-corrosion composite coating, the anti-corrosion composite coating comprising a silver-loaded antibacterial layer and an anti-cosmetic corrosion layer.

[0012] Optionally, the silver-loaded antibacterial layer is prepared using a silver-loaded antibacterial coating solution; the preparation method of the silver-loaded antibacterial coating solution is as follows: take mesoporous silica nanoparticles as a silver ion carrier, add deionized water, and disperse by ultrasonic to prepare a 10-20 g / L mesoporous carrier dispersion liquid; add silver nitrate at 2-3 wt% of the total mass of the coating solution, and fix the silver ions in the pores by magnetic stirring; add 0.8-1.2 g / L aminotri (methylene) phosphonic acid, stir for 10-20 min, and form a stable complex with free silver ions; select a modified water-based acrylic resin as a binder, add 40-50 wt% of the total mass of the coating solution, and stir for 15-25 min; add 0.5-0.8 wt% of a polycarboxylate dispersant and 0.3-0.5 wt% of an organic silicon defoaming agent, disperse in a high-speed dispersing machine, and assist with ultrasonic treatment for 10-20 min during the process to ensure uniform dispersion of each component; adjust the viscosity of the coating solution to 18-22 mPa·s with deionized water, and filter to remove impurities.

[0013] Optionally, the anti-cosmetic corrosion layer is prepared using an anti-corrosion coating solution; the preparation method of the anti-corrosion coating solution is specifically as follows: select a fluorine-silicon modified polyurethane-acrylic composite resin as a base material, add microcapsules at 10-12 wt% of the total mass of the coating solution, and disperse by ultrasonic for 25-35 min; add 0.6-0.9 wt% of a polyether modified polysiloxane leveling agent and 0.3-0.5 wt% of an organic silicon defoaming agent, disperse in a high-speed dispersing machine for 40-60 min, and assist with ultrasonic treatment for 15-25 min during the process; adjust the viscosity of the coating solution to 25-30 mPa·s with an environmentally friendly solvent, and filter to remove impurities;

[0014] The preparation method of the microcapsule is as follows: the core material is selected as 12-15wt% thiourea derivative+8-10wt% dissolved in anhydrous ethanol to form a core material solution; the shell material is selected as polyurethane-polysiloxane composite elastomer, the core material solution is dropped into the shell material prepolymer according to the weight ratio of 1:4, stirring at (30-40) ±2℃ for 0.5-1.5h; deionized water is added to adjust the solid content of the system to 30wt%, the pH value is adjusted to 7-8, and the in-situ polymerization reaction is started for 2-3h; centrifugal separation, deionized water washing and vacuum drying are carried out to obtain microcapsules with a particle size of 2-4μm.

[0015] In a second aspect, the application provides a preparation method of a silver-copper alloy precision component corrosion-resistant composite coating, which adopts the following technical scheme:

[0016] The preparation method of a silver-copper alloy precision component corrosion-resistant composite coating specifically comprises the following steps:

[0017] (1) Substrate pretreatment: sequentially performing oil removal treatment and surface etching treatment on the silver-copper alloy component to prepare a chemical pretreatment layer;

[0018] (2) Preparation of silver-loaded antibacterial layer: forming a silver-loaded antibacterial layer on the surface of the pretreated silver-copper alloy substrate by using a silver-loaded antibacterial coating solution; the preparation method of the silver-loaded antibacterial coating solution is as follows: taking mesoporous silica nanoparticles as a silver ion carrier, adding deionized water, and performing ultrasonic dispersion to prepare a 10-20g / L mesoporous carrier dispersion liquid; adding silver nitrate at 2-3wt% of the total mass of the coating solution, and fixing the silver ions in the pores by magnetic stirring; selecting a modified water-based acrylic resin as a binder, and adding it at 40-50wt% of the total mass of the coating solution, and stirring for 15-25min; adding 0.5-0.8wt% of a polycarboxylate dispersant and 0.3-0.5wt% of an organic silicon defoaming agent, and placing them in a high-speed dispersion machine for dispersion, and supplementing ultrasonic treatment for 10-20min during the dispersion to ensure uniform dispersion of the components; adjusting the viscosity of the coating solution to 18-22mPa·s by using deionized water, and filtering to remove impurities;

[0019] (3) Preparation of a cosmetic corrosion-resistant layer: continuously forming a cosmetic corrosion-resistant layer on the surface of the substrate by using a corrosion-resistant coating solution;

[0020] The preparation method of the corrosion-resistant coating solution is specifically as follows: selecting a fluorine-silicon modified polyurethane-acrylic composite resin as a base material, adding microcapsules at 10-12wt% of the total mass of the coating solution, and performing ultrasonic dispersion for 25-35min; adding 0.6-0.9wt% of a polyether modified polysiloxane leveling agent and 0.3-0.5wt% of an organic silicon defoaming agent, and placing them in a high-speed dispersion machine for dispersion for 40-60min, and supplementing ultrasonic treatment for 15-25min during the dispersion; adjusting the viscosity of the coating solution to 25-30mPa·s by using an environmentally friendly solvent, and filtering to remove impurities;

[0021] The preparation method of the microcapsule is as follows: the core material is selected from 12-15wt% thiourea derivative+8-10wt% dissolved in anhydrous ethanol to form a core material solution; the shell material is selected from polyurethane-polysiloxane composite elastomer, the core material solution is dropped into the shell material prepolymer according to a weight ratio of 1:4, stirring at (30-40)±2℃ for 0.5-1.5h; deionized water is added to adjust the solid content of the system to 30wt%, the pH is adjusted to 7-8, and the in-situ polymerization reaction is started for 2-3h; centrifugal separation, deionized water washing, vacuum drying are performed to obtain microcapsules with a particle size of 2-4μm.

[0022] (4) Post-processing: low-temperature curing and surface polishing are performed on the prepared silver-copper alloy component top layer to obtain a corrosion-resistant composite coating on the surface of the silver-copper alloy component.

[0023] The application removes the oxide layer and impurities on the surface of the silver-copper alloy component through substrate pretreatment, while avoiding excessive corrosion of the silver-copper alloy. Through the preparation of the silver-loaded antibacterial layer, a silver-loaded antibacterial layer is formed on the surface of the pretreated substrate, achieving inhibition of common pathogenic bacteria. Through the preparation of the anti-cosmetic corrosion layer, the penetration of corrosion components in cosmetics is blocked, and the chemical pretreatment layer improves the adhesion of the coating. Through post-processing, the coating surface is smooth and compatible with the decorative properties of the silver-copper alloy component.

[0024] The chemical pretreatment layer breaks through the traditional "single roughening" logic and introduces the "deep cleaning-synergistic corrosion control-active modification" three mechanisms. Through the use of environmentally friendly degreasing agents, impurities are completely removed, and a composite synergistic micro-etching solution is used to achieve simultaneous micro-etching of silver and copper. Silane coupling agents introduce active functional groups to build a "clean surface+uniform roughness+chemical activity" pretreatment defense line.

[0025] The "phosphoric acid+trace nitric acid" in the composite synergistic micro-etching solution provides a mild etching environment. Phosphoric acid forms soluble complexes with Ag⁺ and Cu²⁺, avoiding local nodules. ATMP complexes free metal ions, inhibiting autocatalytic corrosion and solving the problem of "copper preferential over-corrosion" caused by the potential difference between silver and copper. BTA adsorbs and protects the silver surface, and phytic acid introduces hydroxyl and phosphate active functional groups. Finally, a uniform micro-rough layer (Ra=0.10-0.15μm) with a thickness of 0.3-0.6μm is formed. Compared with traditional dilute nitric acid micro-etching, the adhesion is improved by 1-2 levels (from 4B+ to 5B+). The ethanol solution of silane coupling agent KH-560 forms a siloxane bonding layer on the etched surface through hydrolysis reaction. The uniformly distributed hydroxyl groups form chemical bonds with the amino and carboxyl groups of the subsequent coating, significantly improving the interfacial adhesion between the coating and the substrate. Test results show that after treatment by this layer, the cross-hatch adhesion is stable at 5B+ level, and the retention rate after dynamic friction is ≥95%.

[0026] The silver-loaded antibacterial layer breaks through the traditional logic of "single silver loading + physical bonding" and introduces a three-mechanism approach of "mesoporous adsorption - complexation stabilization - chemical bonding". It fixes silver ions through a mesoporous carrier, enhances stability with ATMP, and strengthens interfacial bonding with a modified binder, thus constructing a functional defense line of "long-lasting antibacterial effect + uniform dispersion + strong adhesion".

[0027] Mesoporous silica nanoparticles (50-80 nm in diameter, specific surface area ≥800 m² / g) physically adsorb silver ions through their porous structure, preventing free aggregation. ATMP forms a stable complex with free silver ions, controlling the slow release of silver ions. This ensures an antibacterial rate of ≥99.5% (against Escherichia coli and Staphylococcus aureus) after 24 hours and maintains an antibacterial rate of ≥99.0% after 50 water cycles, overcoming the shortcomings of traditional silver-loaded layers that exhibit "short-term antibacterial properties followed by rapid failure." Segmented processing using ultrasonic dispersion and a high-speed disperser ensures uniform distribution of the mesoporous carrier and silver ions, eliminating agglomerates with a particle size ≥1 μm (verified by SEM observation). The high compatibility of the modified waterborne acrylic resin further inhibits silver ion migration and precipitation, resulting in a relative standard deviation (RSD) of silver element distribution on the coating surface of ≤5%, preventing localized antibacterial failure or coating defects. The waterborne acrylic resin modified with KH-550 introduces amino functional groups, which form chemical bonds with the hydroxyl and phosphate groups of the chemical pretreatment layer, replacing the traditional physical bonding. The electrostatic assisted dip coating method (3~5kV voltage) allows the coating liquid to adhere tightly to the gaps and corners of the components. The gradient drying process (pre-drying → preliminary cross-linking → vacuum drying) avoids solvent residue, ultimately achieving a cross-cut adhesion strength of 5B+ level, with a decrease rate of ≤8% after dynamic cycling.

[0028] The anti-corrosion coating for cosmetics breaks through the traditional logic of "single resin barrier" and introduces a synergistic design of "dense barrier-targeted adsorption-self-repair". It improves corrosion resistance through fluorinated silicone modified resin, achieves targeted protection through sulfide adsorption microcapsules, and ensures coating uniformity through electrostatic assisted atomization spraying, thus building a top-level defense line of "strong barrier + anti-sulfurization + high gloss".

[0029] In fluorinated silicone-modified polyurethane-acrylic composite resin, the fluorine groups provide strong hydrophobicity, blocking the penetration of polar corrosive components (sodium sulfide, lactic acid, sodium hydroxide) in cosmetics; the silicone groups enhance the resin's crosslinking density and flexibility, preventing coating cracking caused by friction. Test results show that this resin system achieves a static corrosion rate ≤0.003 g / (m²·h), far superior to ordinary polyurethane-modified acrylic resin (0.012 g / (m²·h)). The thiourea derivative core material of sulfide-adsorbing microcapsules (particle size 2~4 μm) specifically adsorbs sulfides in cosmetics, preventing them from reacting with silver-copper alloys to form sulfide spots; benzotriazole further inhibits silver-copper oxidation; when the coating is scratched by friction, the elastic shell (elastic modulus 10~15 MPa) ruptures, releasing the core material and quickly filling defects, resulting in a sulfide spot coverage rate ≤0.1% and a corrosion propagation rate ≤0.008 mm / h after dynamic cycling. Electrostatic assisted atomization spraying (6~8kV voltage, 8~12μm atomized particle size) combined with the "horizontal and vertical cross + oblique replenishment spraying" process ensures that the coating uniformly covers complex components. The multi-coat thin coating and pre-curing avoid pinholes and solvent residue. Dry polishing with a 3000-mesh sponge wheel and wet polishing with silica polishing liquid make the coating Ra≤0.06μm, the gloss at a 60° angle ≥88GU (close to the original gloss of silver-copper alloy 90GU), and the gloss retention rate reaches 96%, solving the pain point of "covering up the gloss" of traditional coatings.

[0030] Optionally, the silver-loaded antibacterial coating solution also includes aminotrimethylenephosphonic acid, with an addition amount of 0.5-1.5 g / L; the addition is made after the addition of silver nitrate.

[0031] Optionally, the amount of aminotrimethylenephosphonic acid added is 0.8-1.2 g / L.

[0032] Optionally, the concentration of the mesoporous support dispersion is 12-18 g / L.

[0033] Optionally, the thickness of the silver-loaded antibacterial layer is 8~10μm.

[0034] Optionally, the thickness of the anti-corrosion layer for cosmetics is 12~15μm.

[0035] Optionally, a chemical pretreatment layer is prepared using a composite synergistic micro-etching solution; the formulation of the composite synergistic micro-etching solution is as follows: 8~10 vol% phosphoric acid, 1~2 vol% nitric acid, 3~5 g / L aminotrimethylenephosphonic acid, 0.8~1.2 g / L benzotriazole, 2~3 g / L phytic acid; the solvent is deionized water.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] (1) Excellent anti-corrosion performance of cosmetics: The anti-corrosion layer can effectively resist the erosion of sulfides, acid and alkali components in perfumes, foundations and other cosmetics. There are no corrosion spots or loss of gloss after long-term contact.

[0038] (2) Significant antibacterial effect: The silver-loaded antibacterial layer has an antibacterial rate of over 99% against common pathogens such as Escherichia coli and Staphylococcus aureus, thus solving the hygiene and safety hazards of close-fitting use.

[0039] (3) Strong coating adhesion: The chemical pretreatment layer and the three-layer composite structure design ensure a tight bond between the coating and the silver-copper alloy substrate. It is not easy to fall off due to friction during carrying, and the protection is long-lasting.

[0040] (4) Retain the original metallic luster: The coating has good transparency and does not obscure the original metallic luster of the silver-copper alloy, so the decorative effect is not affected.

[0041] (5) Suitable for portable use scenarios: The coating is thin and light, which does not affect the feel and user experience of the components, and meets the requirements of portable precision components. Detailed Implementation

[0042] Before describing the embodiments of this application in detail, it should be understood that the terminology used herein is for the purpose of describing a particular embodiment only. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the term pertains.

[0043] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0044] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0046] This application provides a silver-copper alloy precision component anti-corrosion composite coating and its preparation method. The anti-corrosion composite coating includes a silver-loaded antibacterial layer and a cosmetic corrosion-resistant layer.

[0047] This application also provides a method for preparing a corrosion-resistant composite coating for silver-copper alloy precision components.

[0048] In one specific embodiment, the preparation method includes the following steps:

[0049] (a) Substrate pretreatment

[0050] (1) Degreasing treatment

[0051] Immerse the silver-copper alloy components in a degreasing agent and treat them for 5-8 minutes at 40-50℃ and ultrasonic power of 300-500W. For complex, irregularly shaped components, the treatment time can be extended to 8-12 minutes. During this time, gently brush the crevices manually (using a soft nylon brush) to ensure thorough removal of oil stains. After degreasing, rinse with deionized water for 2-3 minutes. The surface water film should be continuous and unbroken to indicate successful degreasing; if the water film breaks, degreasing must be repeated.

[0052] The degreasing agent used is an environmentally friendly alkaline degreasing agent (composed of 50-80 g / L sodium carbonate (industrial grade, purity ≥98%), 20-30 g / L trisodium phosphate (industrial grade, purity ≥98%), and 5-10 g / L nonionic surfactant (industrial grade, polyoxyethylene ether), pH value 10-12). The use of an environmentally friendly alkaline degreasing agent to replace traditional solvent-based degreasing agents reduces VOC emissions.

[0053] (2) Surface micro-etching treatment

[0054] The degreased silver-copper alloy components were immersed in a composite synergistic micro-etching solution and treated for 15-25 seconds at 25±2℃ and 200-250W ultrasonic assistance, with the container gently shaken every 5 seconds to ensure uniform micro-etching. Immediately after micro-etching, the components were ultrasonically rinsed with deionized water for 4-6 minutes (300W power, 40kHz frequency) to remove residual micro-etching solution and complexation products from the surface. Subsequently, the components were immersed in an ethanol-water solution of 1-2 g / L silane coupling agent KH-560 (ethanol:deionized water = 3:7, volume ratio) at room temperature for 3-5 minutes to modify the surface activity. Finally, the components were dehydrated with anhydrous ethanol and dried with hot air at 60±5℃ for 8-10 minutes to obtain a chemical pretreatment layer.

[0055] The formulation of the composite synergistic micro-etching solution is as follows:

[0056] Weak oxidizing acid system: 8~10 vol% phosphoric acid (analytical grade, 85%) + 1~2 vol% nitric acid (analytical grade, purity ≥98%); metal ion complexing agent: 3~5 g / L aminotrimethylenephosphonic acid (ATMP, industrial grade, purity ≥95%); silver-based corrosion inhibitor: 0.8~1.2 g / L benzotriazole (BTA, analytical grade, purity ≥99%); active site modifier: 2~3 g / L phytic acid (analytical grade, 70%); solvent is deionized water (conductivity ≤10 μS / cm).

[0057] Phosphoric acid provides a mild etching environment, forming soluble complexes with silver and copper ions to prevent localized nodule formation. A trace amount of nitric acid supplements the oxidizing properties, ensuring a uniform etching rate and replacing the strong corrosive properties of traditional concentrated nitric acid. Metal ion complexing agents precisely complex the Ag⁺ and Cu²⁺ generated during micro-etching, reducing the concentration of free metal ions in the solution, inhibiting "autocatalytic corrosion," and preventing preferential excessive corrosion of copper in silver-copper alloys (solving the problem of uneven etching caused by the potential difference between silver and copper). Benzotriazole forms a dense adsorption film on the silver surface, protecting silver from excessive etching while not affecting moderate micro-etching of copper, thus balancing the preservation of silver's luster with the activation of copper etching. Phytic acid forms a multi-component complex layer on the metal surface, introducing active functional groups such as hydroxyl and phosphate groups during micro-etching, providing chemical bonding sites for subsequent coatings, overcoming the limitation of traditional micro-etching which only creates a physically rough surface.

[0058] After treatment, a light golden-yellow uniform micro-rough layer is formed on the substrate surface. The micro-etching depth is precisely controlled at 0.3~0.6μm, the surface roughness Ra=0.10~0.15μm, and the surface is uniformly distributed with active functional groups such as hydroxyl (-OH) and phosphate ester (-PO3H2), without local over-corrosion or pitting defects.

[0059] (II) Preparation of silver-loaded antibacterial layer

[0060] (1) Preparation of silver-loaded antibacterial coating solution

[0061] A stable silver-loaded antibacterial coating solution was prepared based on the core principles of "long-lasting sustained release of silver ions + uniform dispersion + strong interfacial bonding," as detailed below:

[0062] Mesoporous silica nanoparticles (industrial grade, particle size 50~80nm, specific surface area ≥800m² / g) were used as silver ion carriers and added to deionized water (conductivity ≤10μS / cm). The mixture was ultrasonically dispersed at 350-450W for 15-25min (frequency 40kHz) to obtain a 10~20g / L mesoporous carrier dispersion.

[0063] Add silver nitrate (analytical grade, purity ≥99.5%) at 2-3 wt% of the total mass of the coating solution, and stir magnetically for 25-35 min at (25-35) ± 2℃ (stirring rate 200-400 r / min). The silver ions are fixed in the pores by the adsorption of the mesoporous material, thus avoiding free aggregation.

[0064] Add 0.5~1.5g / L aminotrimethylenephosphonic acid (ATMP, industrial grade, purity ≥9.5%), stir for 10-20min to form a stable complex with free silver ions, further inhibiting the precipitation and aggregation of silver ions;

[0065] Modified waterborne acrylic resin (industrial grade, solid content 45%, modified with silane coupling agent KH-550 to introduce amino functional groups) was selected as the binder and added at 40~50wt% of the total mass of the coating liquid. The mixture was stirred for 15-25min (stirring speed 200-400r / min).

[0066] Add 0.5~0.8wt% polycarboxylate dispersant (industrial grade, solid content ≥30%) and 0.3~0.5wt% silicone defoamer (industrial grade, active ingredient ≥15%), and place in a high-speed disperser to disperse at 1600-2000r / min for 35-45min, supplemented by ultrasonic treatment at 250-350W for 10-20min (ultrasonic treatment for 5min every 10min of dispersion to avoid local overheating) to ensure uniform dispersion of all components;

[0067] The viscosity of the coating solution was adjusted to 18~22 mPa·s with deionized water (tested with a rotational viscometer at 25℃), and impurities were removed by filtration through a 0.45 μm filter membrane.

[0068] Storage and use: Store in a sealed, light-proof container at room temperature. Prepare and use immediately (coating should be completed within 4 hours of preparation). Before use, the mixture must be ultrasonically dispersed at 200W for 5 minutes to ensure no secondary agglomeration.

[0069] (2) Coating and film formation operation

[0070] Coating environment control: cleanliness level ≤ 100,000, ambient humidity 40~55%RH, to avoid impurities and moisture affecting coating uniformity; verification after substrate pretreatment: surface oil residue ≤ 3mg / m² (gravimetric test), no visible oxidation spots, to ensure the foundation of coating adhesion.

[0071] Electrostatic assisted dip coating method: The pretreated silver-copper alloy component is used as the cathode and the stainless steel plate is used as the anode (10cm apart). A 3~5kV electrostatic voltage is applied and the component is immersed in the above coating liquid (the liquid level is 5cm higher than the component). After immersion for 30~40s, the component is lifted at a uniform speed of 5~6cm / min. The electrostatic adsorption effect is used to make the coating liquid evenly adhere to the surface of the component (including gaps and corners).

[0072] Gradient drying process: First, pre-dry with hot air at (45-55) ±2℃ for 10-20 min to remove surface moisture; then raise the temperature to (65-75) ±2℃ and hold for 15-25 min to promote the initial cross-linking of the binder; finally, vacuum dry at (80-90) ±2℃ for 5-15 min (vacuum degree -0.08~-0.09MPa) to completely remove residual solvent and avoid silver ion migration and precipitation.

[0073] Film control: The dry film thickness of the silver-loaded antibacterial layer is precisely controlled to be 8~10μm (tested with a coating thickness gauge, taking the average value of 5 measuring points), and the surface roughness Ra=0.08~0.12μm (tested with a stylus roughness tester, referring to GB / T 3505-2009), with no obvious particles and pinholes.

[0074] (III) Preparation of Anti-corrosion Layer for Cosmetics

[0075] (1) Preparation of anti-corrosion coating liquid

[0076] Based on the core principles of "high barrier properties + self-healing + gloss retention", an anti-corrosion coating liquid for cosmetics was prepared, as detailed below:

[0077] Fluorine-silicone modified polyurethane-acrylic composite resin (industrial grade, solid content 40%, fluorine content 5~8wt%, silicon content 3~5wt%, glass transition temperature Tg=20~30℃) is selected as the base material to balance hydrophobicity and flexibility, and improve the barrier properties against sulfides, acids and alkalis.

[0078] Preparation and addition of sulfide-adsorbed microcapsules:

[0079] 1. The core material is made of 12-15 wt% thiourea derivative (industrial grade, purity ≥98%, which can specifically adsorb sulfides in cosmetics) + 8-10 wt% benzotriazole (industrial grade, purity ≥99%, which inhibits silver and copper oxidation), dissolved in anhydrous ethanol (analytical grade, purity ≥99.7%) to form a core material solution (total core material concentration 20 wt%).

[0080] 2. The shell material is selected from polyurethane-polysiloxane composite elastomer (industrial grade, NCO content 8~10%). The core material solution is dropped into the shell material prepolymer (core material: shell material = 1: (3-5), mass ratio), and stirred at (30-40) ±2℃ for 0.5-1.5h (stirring speed 300-400r / min).

[0081] 3. Add deionized water to adjust the solid content of the system to 30wt%, adjust the pH to 7-8, and start the in-situ polymerization reaction for 2-3 hours;

[0082] 4. After centrifugation (8000-10000 r / min, 10-15 min), washing with deionized water 2-3 times (until the washing solution pH=7), and vacuum drying at 50-70℃ for 5-7 h, microcapsules with a particle size of 2-4 μm (shell thickness 0.2-0.4 μm, elastic modulus 10-15 MPa, suitable for friction scenarios) are obtained.

[0083] Add microcapsules at 10-12 wt% of the total mass of the coating liquid, and disperse by ultrasonication at 300-400W for 25-35 minutes (frequency 40kHz) to ensure uniform dispersion without agglomeration.

[0084] Add 0.6~0.9wt% polyether-modified polysiloxane leveling agent (industrial grade, active ingredient ≥20%) and 0.3~0.5wt% silicone defoamer (industrial grade, active ingredient ≥15%), and place in a high-speed disperser to disperse at 1800-2000r / min for 40-60min, supplemented by ultrasonic treatment at 300-350W for 15-25min (ultrasonic treatment for 5min every 15min of dispersion).

[0085] Adjust the viscosity of the coating solution to 25~30 mPa·s (tested with a rotational viscometer at 25℃) using an environmentally friendly solvent (ethanol:deionized water = 1:4, volume ratio, VOC content ≤30g / L). Filter through a 0.45μm filter membrane and prepare immediately before use (coating should be completed within 6 hours of preparation). Before use, ultrasonically disperse the solution for 3-6 minutes at 200-300W.

[0086] (2) Spray coating film formation operation

[0087] Coating environment control: cleanliness level ≤ 100,000, ambient humidity 40~50% RH, temperature 25±2℃, to avoid excessive humidity causing coating blistering;

[0088] Electrostatic assisted atomization spraying method is adopted: spray gun pressure 0.2~0.3MPa, applied electrostatic voltage 6~8kV, spraying distance 22~25cm, atomized particle size 8~12μm (tested by laser particle size analyzer); complex irregular components adopt the "horizontal and vertical cross + oblique supplementary spraying" method, with two thin coats, each with a dry film thickness of 6~7.5μm. After each coat, pre-curing is carried out at 55±2℃ for 12~15min (hot air velocity 0.8~1.2m / s) to remove solvent and moisture.

[0089] The thickness of the top dry film is controlled at 12~15μm (measured by a coating thickness gauge, taking the average value of 5 measuring points), forming a composite coating with a total thickness of 20~25μm with the intermediate layer (balancing protection and gloss retention).

[0090] (iv) Post-processing

[0091] (1) Low temperature curing

[0092] After the top layer of the silver-copper alloy component is prepared, it is placed in a hot air circulating oven and cured in a stepped low temperature manner: first, it is preheated at 50-60℃ for 10-15 minutes, then the temperature is raised to 120-140℃ and held for 30-40 minutes, and finally the temperature is lowered to below 60℃ and removed. This is to avoid oxidation and discoloration of the silver-copper alloy material caused by high temperature curing. Nitrogen gas (oxygen content ≤0.5%) needs to be introduced into the oven for protection to further prevent silver oxidation.

[0093] (2) Surface polishing

[0094] Mechanical-chemical composite polishing is adopted. First, dry polishing is performed for 1-2 minutes with a 3000-mesh sponge polishing wheel (rotation speed 800~1000r / min) and polishing pressure ≤0.1MPa to remove tiny particles on the coating surface. Then, wet polishing is performed for 30-60 seconds with a soft polishing pad containing 0.5~1μm silica polishing liquid (rotation speed 500~600r / min) to avoid excessive pressure from damaging the coating.

[0095] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0096] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0097] The present application will be further described in detail below with reference to the embodiments and test results.

[0098] Example 1

[0099] This embodiment provides a silver-copper alloy precision component anti-corrosion composite coating. The anti-corrosion composite coating includes a silver-loaded antibacterial layer and a cosmetic corrosion-resistant layer. The preparation method of this anti-corrosion composite coating specifically includes the following steps (some parameters are shown in Table 1):

[0100] (a) Substrate pretreatment

[0101] (1) Degreasing treatment

[0102] The silver-copper alloy components were immersed in an environmentally friendly alkaline degreasing agent (composed of 65g / L sodium carbonate, 25g / L trisodium phosphate, and 8g / L nonionic surfactant, pH 10-12) and treated for 6 minutes at 45℃ and 400W ultrasonic power, supplemented by light manual brushing of crevices to ensure complete removal of oil stains. After degreasing, the components were rinsed with deionized water for 3 minutes. The surface water film should be continuous without breaks to indicate successful degreasing; if the water film breaks, degreasing must be repeated.

[0103] (2) Surface micro-etching treatment

[0104] The degreased silver-copper alloy components were immersed in a composite synergistic micro-etching solution and treated for 20 seconds at 25±2℃ and 200W ultrasonic assistance, with the container gently shaken every 5 seconds to ensure uniform micro-etching. Immediately after micro-etching, the components were ultrasonically rinsed with deionized water for 5 minutes (300W power, 40kHz frequency) to remove residual micro-etching solution and complexation products from the surface. Subsequently, the components were immersed in an ethanol-water solution of 1.5g / L silane coupling agent KH-560 (ethanol:deionized water volume ratio of 3:7) at room temperature for 5 minutes to perform surface activity modification. Finally, the components were dehydrated with anhydrous ethanol and dried with hot air at 60±5℃ for 10 minutes to obtain a chemical pretreatment layer.

[0105] The formulation of the composite synergistic micro-etching solution is as follows: 9 vol% phosphoric acid, 1.5 vol% nitric acid, 4 g / L aminotrimethylenephosphonic acid, 1 g / L benzotriazole, and 2.5 g / L phytic acid; the solvent is deionized water.

[0106] (II) Preparation of silver-loaded antibacterial layer

[0107] (1) Preparation of silver-loaded antibacterial coating solution

[0108] Mesoporous silica nanoparticles were used as silver ion carriers and added to deionized water. The mixture was ultrasonically dispersed at 400W for 20 min (frequency 40kHz) to obtain a 10 g / L mesoporous carrier dispersion. Silver nitrate was added at 2.5 wt% of the total coating solution, and the mixture was magnetically stirred at 30±2℃ for 30 min (stirring rate 300 r / min). The silver ions were fixed within the pores through adsorption by the mesoporous material, preventing free aggregation. Modified waterborne acrylic resin (industrial grade, 45% solids content, modified with silane coupling agent KH-550 to introduce amino functional groups) was selected as the carrier. As a binder, add 45wt% of the total mass of the coating liquid and stir for 20 min (stirring speed 300 r / min); add 0.6wt% polycarboxylate dispersant and 0.4wt% silicone defoamer, and place in a high-speed disperser to disperse at 1800 r / min for 40 min, during which time it is supplemented with 300W ultrasonic treatment for 15 min (ultrasonic treatment for 5 min every 10 min of dispersion to avoid local overheating) to ensure uniform dispersion of each component; adjust the viscosity of the coating liquid to 18~22 mPa·s with deionized water, and filter through a 0.45μm filter membrane to remove impurities.

[0109] (2) Coating and film formation operation

[0110] An electrostatic assisted dip-coating method was adopted: The pretreated silver-copper alloy component was used as the cathode, and a stainless steel plate as the anode (10cm apart). A 3-5kV electrostatic voltage was applied, and the component was immersed in the coating solution (liquid level 5cm above the component). After immersion for 30-40 seconds, it was lifted at a uniform speed of 5-6cm / min, utilizing electrostatic adsorption to ensure the coating solution adhered evenly to the component surface (including gaps and corners). A gradient drying process was followed: First, hot air pre-drying was performed at 50±2℃ for 15 minutes to remove surface moisture; then, the temperature was raised to 70±2℃ and held for 20 minutes to promote initial cross-linking of the binder; finally, vacuum drying was performed at 85±2℃ for 10 minutes (vacuum degree -0.08~-0.09MPa) to thoroughly remove residual solvent and prevent silver ion migration and precipitation. The film thickness was adjusted by regulating the immersion time.

[0111] (III) Preparation of Anti-corrosion Layer for Cosmetics

[0112] (1) Preparation of anti-corrosion coating liquid

[0113] Fluorine-silicone modified polyurethane-acrylic composite resin (industrial grade, solid content 40%, fluorine content 5-8wt%, silicon content 3-5wt%, glass transition temperature Tg=20-30℃) was selected as the base material. Microcapsules were added at 10wt% of the total mass of the coating liquid and ultrasonically dispersed at 350W for 30min (frequency 40kHz) to ensure uniform dispersion without agglomeration. 0.8wt% polyether-modified polysiloxane leveling agent and 0.3-0.5wt% silicone defoamer were added and dispersed in a high-speed disperser at 2000r / min for 50min, supplemented by ultrasonic treatment at 300W for 20min (ultrasonic treatment for 5min every 15min of dispersion). The viscosity of the coating liquid was adjusted to 25-30mPa·s with an environmentally friendly solvent (ethanol:deionized water volume ratio 1:4, VOC content ≤30g / L). The mixture was filtered through a 0.45μm filter membrane and ultrasonically dispersed at 250W for 5min before use.

[0114] Preparation and addition of sulfide-adsorbed microcapsules:

[0115] 1. The core material is made of 13wt% thiourea derivative + 8~10wt% benzotriazole, dissolved in anhydrous ethanol to form a core material solution;

[0116] 2. The shell material is selected as polyurethane-polysiloxane composite elastomer. The core material solution is dropped into the shell material prepolymer (core material: shell material = 1:4, mass ratio), and stirred at 35±2℃ for 1h (stirring speed 350r / min).

[0117] 3. Add deionized water to adjust the solid content of the system to 30wt%, adjust the pH to 7-8, and start the in-situ polymerization reaction for 2.5h;

[0118] 4. After centrifugation (9000 r / min, 12 min), washing with deionized water 3 times (until the washing solution pH=7), and vacuum drying at 60℃ for 6 h, microcapsules with a particle size of 2~4 μm (shell thickness 0.2~0.4 μm, elastic modulus 10~15 MPa) were obtained.

[0119] (2) Coating film forming process

[0120] Electrostatic assisted atomization spraying method is adopted: spray gun pressure 0.25MPa, applied electrostatic voltage 6~8kV, spraying distance 22~25cm, atomized particle size 8~12μm; two thin coats are applied, and after each coat, pre-curing is carried out at 55±2℃ for 12~15min (hot air velocity 1m / s) to remove solvent and moisture. The film thickness is adjusted by controlling the thickness of each spraying coat.

[0121] (iv) Post-processing

[0122] (1) Low temperature curing

[0123] After the top layer of the silver-copper alloy component is prepared, it is placed in a hot air circulating oven and cured in a stepped low temperature manner: first, it is preheated at 60℃ for 10 minutes, then the temperature is raised to 130℃ and held for 30 minutes, and finally the temperature is lowered to below 60℃ and removed. This is to avoid the silver-copper alloy material from oxidizing and discoloring due to high temperature curing. Nitrogen gas (oxygen content ≤0.5%) needs to be introduced into the oven for protection to further prevent silver oxidation.

[0124] (2) Surface polishing

[0125] Mechanical-chemical composite polishing is adopted. First, dry polishing is performed for 1~2 minutes with a 3000-mesh sponge polishing wheel (1000 r / min) at a polishing pressure ≤0.1 MPa to remove tiny particles on the coating surface. Then, wet polishing is performed for 40 seconds with a soft polishing pad containing 0.5 μm silica polishing liquid (500 r / min) to avoid excessive pressure from damaging the coating.

[0126] Example 2-14

[0127] Examples 2-14 provide a corrosion-resistant composite coating for silver-copper alloy precision components. The difference between the above corrosion-resistant composite coating preparation methods lies in the different parameters during the preparation process, as shown in Table 1. The remaining operation steps are consistent with the corresponding examples.

[0128] Specifically, the differences between Examples 1-14 are as follows:

[0129] The difference between Examples 1-5 is the concentration of the mesoporous carrier dispersion.

[0130] The difference between Examples 3 and 6-10 is that: after adding silver nitrate, the silver-loaded antibacterial coating liquid also contains aminotrimethylenephosphonic acid, and is stirred for 15 minutes; and the amount of aminotrimethylenephosphonic acid added.

[0131] The difference between Examples 8 and 11-14 is that the film thickness is different.

[0132] Example 15

[0133] This embodiment provides a corrosion-resistant composite coating for silver-copper alloy precision components. The difference between the preparation method of the above corrosion-resistant composite coating and the embodiment is that the micro-etching solution used in the surface micro-etching treatment during substrate pretreatment is different. The remaining operation steps are consistent with those in Embodiment 8.

[0134] In this embodiment, the surface micro-etching treatment is as follows: the degreased component is immersed in dilute nitric acid micro-etching solution (10 vol% nitric acid aqueous solution, analytical grade) and soaked at room temperature for 40 seconds, during which the container is gently shaken to ensure uniform micro-etching; after micro-etching, it is immediately rinsed with deionized water for 3-5 minutes, then dehydrated with anhydrous ethanol and dried at room temperature; after treatment, a light gray uniform rough layer is formed on the surface of the substrate.

[0135] Comparative Examples 1-3

[0136] Comparative Examples 1-3 each provide a silver-copper alloy precision component anti-corrosion composite coating. The difference between the above anti-corrosion composite coating preparation methods lies in the different parameters in the preparation process, as shown in Table 1, while the remaining operation steps are consistent with the corresponding embodiments.

[0137] Specifically, the differences between Example 1 or Example 8 and Comparative Examples 1-3 are as follows:

[0138] The difference between Example 1 and Comparative Examples 1-2 is the concentration of the mesoporous carrier dispersion.

[0139] The difference between Example 8 and Comparative Example 3 is the thickness of the top layer.

[0140] Comparative Example 4

[0141] This comparative example provides a corrosion-resistant composite coating for silver-copper alloy precision components. The preparation method of the above-mentioned corrosion-resistant composite coating differs from that of Example 8 in that the preparation processes of steps (i), (ii), and (iii) are different. However, the remaining operation steps are consistent with those of Example 8.

[0142] (a) Substrate pretreatment

[0143] (2) Surface micro-etching treatment

[0144] The degreased components were immersed in a dilute nitric acid micro-etching solution (10 vol% nitric acid aqueous solution, analytical grade) for 40 seconds at room temperature, during which the container was gently shaken to ensure uniform micro-etching. After micro-etching, the components were immediately rinsed with deionized water for 3-5 minutes, then dehydrated with anhydrous ethanol and air-dried at room temperature. After treatment, a light gray uniform rough layer was formed on the surface of the substrate.

[0145] (II) Preparation of silver-loaded layer

[0146] Coating solution preparation: Take ordinary water-based acrylic resin (industrial grade, solid content 40%) as binder, add 3~5wt% silver nitrate (analytical grade, silver ion antibacterial agent), stir and mix for 10~15min (without ultrasonic dispersion step) to obtain coating solution; adjust the viscosity to 20~25mPa·s with deionized water to suit the coating process.

[0147] Coating and film formation: The coating liquid is applied to the pretreated substrate surface by dip coating at a speed of 8-10 cm / min. After natural drying at room temperature for 15-20 min, it is then dried with hot air at 65℃ for 15 min to form a silver-loaded layer; the layer thickness is the same as in Example 8.

[0148] (3) Preparation of anti-corrosion coating for cosmetics

[0149] Coating solution preparation: Ordinary polyurethane modified acrylic resin (industrial grade, chemically resistant) is selected as the base material, and environmentally friendly solvent ethyl acetate (analytical grade) is added to adjust the resin solid content to 25%. The mixture is stirred and mixed for 10 minutes to obtain the anti-cosmetic corrosion coating solution.

[0150] Film formation by spraying: The air spraying method is used, with a spray gun pressure of 0.3~0.4MPa and a spraying distance of 25~30cm. The coating liquid is evenly sprayed onto the surface of the antibacterial intermediate layer. Spray 1~2 times, and after each spraying, dry with hot air at 55℃ for 10min to form a cosmetic corrosion-resistant layer. The layer thickness is the same as in Example 8.

[0151] Table 1. Preparation methods and parameters of some examples and comparative examples

[0152]

[0153] Performance testing

[0154] The above embodiments and comparative examples were tested as follows, and the test results are shown in Table 2.

[0155] (a) Resistance to cosmetic corrosion

[0156] (1) Preparation of simulated cosmetic corrosive solution (designed with reference to common cosmetic ingredients and corrosive properties)

[0157] The specific testing method is as follows: Prepare a simulated cosmetic corrosive medium (covering the core corrosive components of perfumes, foundations, and skincare products) according to the following composition: 5.0 g / L sodium sulfide (simulating sulfides), 3.0 g / L lactic acid (simulating acidic components), 1.0 g / L sodium hydroxide (simulating alkaline components), 5.0 g / L ethanol (simulating solvent components), 2.0 g / L stearic acid (simulating oil components), with deionized water as the balance; adjust the pH value to 4.0~8.0 with dilute hydrochloric acid or sodium hydroxide (covering the acidity and alkalinity range of most cosmetics). After preparation, filter through a 0.22 μm filter membrane to remove impurities, seal and store away from light, and use within 24 hours (to avoid oxidation and inactivation of sulfides).

[0158] (2) Static immersion corrosion test (refer to GB / T 10125-2021 for expansion and adaptation to cosmetic corrosion scenarios)

[0159] The specific testing methods are as follows:

[0160] Sample pretreatment: Select silver-copper alloy components with intact coating and no scratches, cut them into 50mm×50mm×2mm samples (for complex components, cut according to the actual use surface), wipe the surface with anhydrous ethanol, and let them air dry naturally.

[0161] Immersion conditions: The sample was completely immersed in the above-mentioned simulated cosmetic corrosion solution. The immersion temperature was controlled at 37±2℃ (simulating human body temperature). The immersion time was set to 24h, 72h, 168h (7 days), and 336h (14 days), respectively. Three parallel samples were set for each cycle.

[0162] Process observation: Every 24 hours, take out the sample, rinse the surface corrosion residue with deionized water, blow dry and observe the appearance of the coating (whether discoloration, blistering, cracking, peeling, sulfide spots appear), and record the corrosion initiation time;

[0163] Performance testing: After immersion, the corrosion rate of the sample was tested (weighing method: accurate weighing before and after immersion, with an accuracy of 0.0001g, and calculation of corrosion mass loss per unit area) and coating integrity (observation with a magnifying glass to see if there are traces of corrosion liquid penetration).

[0164] Judgment criteria: After immersion for 336 hours, if the coating shows no obvious discoloration (color difference ΔE≤1.5, refer to GB / T 11186.3-1989), no blistering / cracking / peeling, and a corrosion rate ≤0.003g / (m²·h), it is considered to have qualified static cosmetic corrosion resistance.

[0165] (3) Dynamic cyclic corrosion detection (simulating the "contact-friction-drying" scenario of personal use, refer to GB / T2423.34-2012)

[0166] The specific testing methods are as follows:

[0167] 1. Cycle design: One cycle is 24 hours and includes 3 phases:

[0168] Contact phase: Immersion in a simulated cosmetic corrosive solution at 37±2℃ for 6 hours (simulating the cumulative time of daily contact with cosmetics);

[0169] Friction stage: The coated surface was rubbed with a cotton fabric (plain weave cotton fabric, weight 180~200g / m², simulating clothing / skin friction) loaded with a 500g weight at a frequency of 10 times / min for 30min (friction stroke 5cm).

[0170] Drying stage: Hot air drying at 60±5℃ for 17.5h (simulating the drying process after being removed from the corrosive environment);

[0171] 2. Number of cycles: Set 15 cycles (total 360 hours, covering long-term portable use scenarios), and observe the coating appearance after each cycle;

[0172] 3. Endpoint test: After the cycle is completed, test the coating adhesion (cross-cut test), gloss, and sulfur spot coverage. Compare with the uncorroded sample and calculate the adhesion reduction rate (≤8%) and gloss retention rate (≥88%).

[0173] 4. Judgment criteria: After 15 cycles, if the coating shows no peeling, no obvious corrosion spots, sulfur spot coverage ≤1%, adhesion ≥4B grade, and gloss retention ≥88%, it is considered to have qualified dynamic cosmetic corrosion resistance.

[0174] (ii) Antibacterial

[0175] (1) Antibacterial rate test (broad spectrum)

[0176] The specific testing methods are as follows: Referring to GB / T 21866-2008 "Determination of Antibacterial Properties of Antibacterial Coatings (Films)" (shaking flask method), the 24-hour antibacterial rate of the coating against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) was tested; referring to GB / T 24346-2009 "Evaluation of Antibacterial Properties of Industrial Products - Plastics, Rubber and Other Non-Porous Materials" (film method), the 24-hour antibacterial rate against Candida albicans (ATCC 10231) was tested.

[0177] (2) Antimicrobial cycle stability test (long-term effect)

[0178] The specific testing method is as follows: Refer to the water cycle test method in GB / T 17657-2013 Test Method for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels; immerse the coating in deionized water at 50℃, change the water every 24 hours, cycle 50 times, and then dry the sample in hot air at 60±5℃ for 10 minutes. Repeat the above antibacterial rate test.

[0179] (iii) Cohesion

[0180] (1) Cross-cut adhesion test

[0181] The specific testing method is as follows: Refer to "GB / T 9286-1998 Cross-cut test for paint and varnish film", use a cross-cut tester to cut 10×10 grids (1mm spacing) on ​​the coating surface, stick on the tape and then peel it off, and observe the grid detachment.

[0182] (2) Adhesion test by circling

[0183] The specific testing method is as follows: Refer to "GB / T 1720-1979 Test Method for Coating Adhesion", use a QFD type adhesion tester to draw circles on the coating surface and observe the coating peeling level inside the circle.

[0184] (iv) Gloss

[0185] (1) Gloss

[0186] The specific testing method is as follows: Refer to "GB / T 9754-2007 Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments"; use a 60° gloss meter to test the surface gloss of the coating (the original gloss of silver-copper alloy is about 90 GU).

[0187] (2) Surface roughness

[0188] The specific testing method is as follows: Referring to "GB / T 3505-2009 Product Geometric Specification (GPS) Surface Structure Profile Method Terminology, Definitions and Parameters" (the test basis for surface roughness parameters), the Ra value of the coating surface is tested using a stylus-type roughness meter. The lower the roughness, the more uniform the gloss.

[0189] Table 2 Test Results

[0190]

[0191] As shown in Table 2, by comparing the technical solutions and test results of Examples 1-5 and Comparative Examples 1-2, it can be seen that the concentration of mesoporous silica nanoparticles plays a key role in the silver ion dispersion of the silver-loaded antibacterial layer: when the concentration is 10-20 g / L (Examples 1-5), the silver ion adsorption and dispersion effect is optimal, the static corrosion rate is as low as 0.0018-0.0028 g / (m²·h), and the antibacterial rate reaches over 99.4%; if the concentration is too low (8 g / L, Comparative Example 1), it will cause silver ion aggregation, and the corrosion rate will increase to 0.0035 g / (m²·h); if the concentration is too high (22 g / L, Comparative Example 2), it will cause a decrease in coating uniformity, and the gloss retention rate will be only 84%.

[0192] By comparing the technical solutions and test results of Examples 3, 6-10, it can be seen that the complexation effect of aminotrimethylenephosphonic acid (ATMP) can enhance the stability of silver ions: when the addition amount is 0.8-1.2 g / L (Examples 7-9), the complexation effect and coating compatibility are balanced, the static corrosion rate is reduced to below 0.0015 g / (m²·h) (1 / 10 of the prior art), ΔE is only 0.7-0.9, and the dynamic gloss retention rate is above 94%; when the addition amount is 0.6 g / L (Example 6), the complexation is insufficient, and when the addition amount is 1.5 g / L (Example 10), the coating adhesion is weakened (reduced to 4B+).

[0193] By comparing the technical solutions and test results of Examples 8, 11-14 and Comparative Example 3, it can be seen that the performance is best when the total film thickness is in the range of 22~25μm: the static corrosion rate of Example 12 (total 23μm) is as low as 0.0011g / (m²·h), and the dynamic sulfurization spot coverage is only 0.1%; if the thickness is too thin (19μm, Comparative Example 3), it will lead to insufficient barrier properties, the static corrosion rate will rise to 0.0038g / (m²·h) and obvious sulfurization spots will appear.

[0194] The technical solutions and test results of Examples 15 and 8 show that the modification effect of the composite synergistic micro-etching solution is significantly better than that of the traditional dilute nitric acid micro-etching solution: the static corrosion rate of Example 15 (traditional micro-etching solution) (0.0023 g / (m²·h)) is 1.9 times that of Example 8, and the adhesion strength is reduced from 5B+ to 4B+, which verifies the core value of "composite micro-etching + silane modification" in improving the adhesion and corrosion resistance of the coating.

[0195] Meanwhile, comparing the technical solutions and test results of Example 4 and Example 8, it can be seen that the existing technology of "traditional micro-etching + ordinary resin + conventional coating" is inferior to the optimized solution in all aspects: Anti-corrosion performance of cosmetics: the static corrosion rate (0.0120g / (m²·h)) is 10 times that of Example 8, ΔE reaches 4.8 (far exceeding the qualified line of 1.5), and dynamic sulfide spots are fully covered; Antibacterial performance: the antibacterial rate is only 95.0% after 24 hours (99.9% in Example 8), and the antibacterial rate drops to 92.0% after 50 water cycles; Adhesion and gloss: the cross-cut adhesion is only 3B, and the gloss is only 75GU (the original gloss of silver-copper alloy is 90GU), which is completely unable to meet the needs of precision components.

[0196] Based on the above, the coating of this application adopts a three-layer composite structure of "chemical pretreatment layer + silver-loaded antibacterial layer + anti-cosmetic corrosion layer", which has excellent anti-cosmetic corrosion and antibacterial properties, while maintaining gloss and having strong adhesion.

[0197] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A corrosion-resistant composite coating for silver-copper alloy precision components, characterized in that, The anti-corrosion composite coating includes a silver-loaded antibacterial layer and a cosmetic corrosion-resistant layer.

2. The anti-corrosion composite coating according to claim 1, characterized in that, The silver-loaded antibacterial layer is prepared using a silver-loaded antibacterial coating solution; the preparation method of the silver-loaded antibacterial coating solution is as follows: Mesoporous silica nanoparticles were used as silver ion carriers and added to deionized water. The mixture was then ultrasonically dispersed to obtain a 10-20 g / L mesoporous carrier dispersion. Silver nitrate was added at 2-3 wt% of the total mass of the coating solution, and the silver ions were fixed in the pores by magnetic stirring. 0.8-1.2 g / L aminotrimethylenephosphonic acid was added and stirred for 10-20 min to form a stable complex with the free silver ions. Modified waterborne acrylic resin is selected as the binder and added at 40-50 wt% of the total mass of the coating liquid. Stir for 15-25 min. Add 0.5-0.8 wt% of polycarboxylate dispersant and 0.3-0.5 wt% of silicone defoamer, and disperse in a high-speed disperser. During the process, ultrasonic treatment is performed for 10-20 min to ensure uniform dispersion of each component. Adjust the viscosity of the coating liquid to 18-22 mPa·s with deionized water and filter to remove impurities.

3. The anti-corrosion composite coating according to claim 1, characterized in that, The anti-corrosion coating layer is prepared using an anti-corrosion coating liquid; the specific preparation method of the anti-corrosion coating liquid is as follows: Fluorosilicone-modified polyurethane-acrylic composite resin was selected as the base material. Microcapsules were added at 10-12 wt% of the total mass of the coating liquid and ultrasonically dispersed for 25-35 min. 0.6-0.9 wt% of polyether-modified polysiloxane leveling agent and 0.3-0.5 wt% of silicone defoamer were added and dispersed in a high-speed disperser for 40-60 min, with ultrasonic treatment for 15-25 min during the process. The viscosity of the coating liquid was adjusted to 25-30 mPa·s with an environmentally friendly solvent, and impurities were removed by filtration. The microcapsules are prepared as follows: the core material is 12-15 wt% thiourea derivative + 8-10 wt%, dissolved in anhydrous ethanol to form a core material solution; the shell material is polyurethane-polysiloxane composite elastomer, and the core material solution is dropped into the shell material prepolymer at a weight ratio of 1:(3-5), and stirred at (30-40)±2℃ for 0.5-1.5h; deionized water is added to adjust the solid content of the system to 30 wt%, the pH is adjusted to 7-8, and the in-situ polymerization reaction is started for 2-3h; Microcapsules with a particle size of 2-4 μm were obtained by centrifugation, washing with deionized water, and vacuum drying.

4. A method for preparing the anti-corrosion composite coating of silver-copper alloy precision components as described in claim 1, characterized in that, The preparation method specifically includes the following steps: (1) Substrate pretreatment: The silver-copper alloy components are subjected to degreasing treatment and surface micro-etching treatment in sequence to obtain a chemical pretreatment layer; (2) Preparation of silver-loaded antibacterial layer: A silver-loaded antibacterial layer is formed on the surface of a pretreated silver-copper alloy substrate using a silver-loaded antibacterial coating liquid; the preparation method of the silver-loaded antibacterial coating liquid is as follows: Mesoporous silica nanoparticles were used as silver ion carriers and added to deionized water. The mixture was then ultrasonically dispersed to obtain a 10-20 g / L mesoporous carrier dispersion. Silver nitrate was added at 2-3 wt% of the total coating solution mass, and the silver ions were fixed within the pores by magnetic stirring. Modified waterborne acrylic resin was selected as a binder and added at 40-50 wt% of the total coating solution mass. The mixture was stirred for 15-25 min. 0.5-0.8 wt% of a polycarboxylate dispersant and 0.3-0.5 wt% of an organosilicon defoamer were added, and the mixture was dispersed in a high-speed disperser, with ultrasonic treatment for 10-20 min to ensure uniform dispersion of all components. The viscosity of the coating solution was adjusted to 18-22 mPa·s with deionized water, and impurities were removed by filtration. The silver-loaded antibacterial coating solution also includes aminotrimethylenephosphonic acid, with an addition amount of 0.5-1.5 g / L; the addition is made after the addition of silver nitrate. (3) Preparation of anti-corrosion coating for cosmetics: The anti-corrosion coating liquid is used to continue to form an anti-corrosion coating on the surface of the substrate; The specific preparation method of the anti-corrosion coating liquid is as follows: Fluorosilicone-modified polyurethane-acrylic composite resin was selected as the base material. Microcapsules were added at 10-12 wt% of the total mass of the coating liquid and ultrasonically dispersed for 25-35 min. 0.6-0.9 wt% of polyether-modified polysiloxane leveling agent and 0.3-0.5 wt% of silicone defoamer were added and dispersed in a high-speed disperser for 40-60 min, with ultrasonic treatment for 15-25 min during the process. The viscosity of the coating liquid was adjusted to 25-30 mPa·s with an environmentally friendly solvent, and impurities were removed by filtration. The microcapsules are prepared as follows: the core material is 12-15 wt% thiourea derivative + 8-10 wt%, dissolved in anhydrous ethanol to form a core material solution; the shell material is polyurethane-polysiloxane composite elastomer, and the core material solution is dropped into the shell material prepolymer at a weight ratio of 1:4, and stirred at (30-40) ± 2℃ for 0.5-1.5 h; deionized water is added to adjust the solid content of the system to 30 wt%, the pH is adjusted to 7-8, and the in-situ polymerization reaction is started for 2-3 h; after centrifugation, washing with deionized water, and vacuum drying, microcapsules with a particle size of 2-4 μm are obtained. (4) Post-treatment: The silver-copper alloy component with the top layer prepared is subjected to low-temperature curing and surface polishing, that is, an anti-corrosion composite coating is obtained on the surface of the silver-copper alloy component.

5. The preparation method according to claim 4, characterized in that, The amount of aminotrimethylenephosphonic acid added is 0.8-1.2 g / L.

6. The preparation method according to claim 4, characterized in that, The concentration of the mesoporous carrier dispersion is 12-18 g / L.

7. The preparation method according to claim 4, characterized in that, The thickness of the silver-loaded antibacterial layer is 8~10μm.

8. The preparation method according to claim 4, characterized in that, The thickness of the anti-corrosion layer for cosmetics is 12~15μm.

9. The preparation method according to claim 4, characterized in that, A chemical pretreatment layer was prepared using a composite synergistic micro-etching solution. The formulation of the composite synergistic micro-etching solution is as follows: 8~10 vol% phosphoric acid, 1~2 vol% nitric acid, 3~5 g / L aminotrimethylenephosphonic acid, 0.8~1.2 g / L benzotriazole, 2~3 g / L phytic acid; the solvent is deionized water.

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