Phosphorus-free nano passivation solution containing modified graphene and preparation method thereof

Abstract

The invention relates to the field of phosphorus-free nano passivation solutions, in particular to a phosphorus-free nano passivation solution containing modified graphene and a preparation method thereof.The preparation method comprises the steps that silane modified graphene oxide dispersion liquid, water-soluble acrylic resin and a silane coupling agent are sequentially dissolved or dispersed in deionized water, finally, the pH is adjusted to 3.5-4.5, the passivation solution is obtained, silane modification is conducted, and the modified graphene-containing phosphorus-free nano passivation solution is obtained. Graphene can be stably dispersed in a passivation solution in a nanosheet layer form and is in directional arrangement parallel to the metal surface in the film forming process to form a labyrinth effect, the diffusion path of a corrosion medium is greatly prolonged, a silane end group on the surface of the modified graphene can form firm chemical bonds with hydroxyl on the metal surface and zirconium and titanium hydrolyzates in the passivation solution, and the corrosion resistance of the metal surface is improved. The problem that the binding force between graphene and a matrix is weak is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of phosphorus-free nano passivation solution, in particular to a phosphorus-free nano passivation solution containing modified graphene and a preparation method thereof. BACKGROUND

[0002] Traditional phosphating and chromate passivation processes contain harmful elements such as phosphorus and chromium, and face severe environmental protection pressure. Although environmental protection technologies such as zirconium-free phosphating and silane treatment have made certain progress, the conversion films formed still have deficiencies in terms of compactness and physical barrier effect, and it is difficult to meet the long-term corrosion protection needs of high-end equipment. Graphene is considered as an ideal corrosion protection material due to its unique two-dimensional sheet structure and excellent chemical stability. However, graphene is prone to agglomeration in the passivation solution system and is difficult to stably disperse, and the adhesion to the metal substrate is weak, so direct application has poor effect, which limits its popularization and application in industrial coating pretreatment. Therefore, a phosphorus-free nano passivation solution containing modified graphene and a preparation method thereof are proposed to exert the barrier advantage of graphene and firmly combine with the metal substrate. SUMMARY

[0003] The present application relates to the field of phosphorus-free nano passivation solution, in particular to a phosphorus-free nano passivation solution containing modified graphene and a preparation method thereof.

[0004] The object of the present application can be achieved by the following technical solutions: A phosphorus-free nano passivation solution containing modified graphene, comprising the following components by weight: 0.1-1.0 parts of silane-modified graphene oxide dispersion liquid, 0.5-2.0 parts of water-soluble acrylic resin, 0.1-1.0 parts of silane coupling agent, and the balance is deionized water, and the pH value of the passivation solution is 3.5-4.5.

[0005] Further, the silane-modified graphene oxide dispersion liquid is prepared by the following method: dispersing graphene oxide in a water-ethanol mixed solvent, adding a silane coupling agent, and refluxing under acidic conditions to make the silane covalently grafted to the surface of the graphene oxide, thereby obtaining a stable silane-modified graphene oxide dispersion liquid.

[0006] Further, the silane coupling agent is gamma-aminopropyl triethoxysilane (KH-550) or gamma-glycidyl ether propyl trimethoxysilane (KH-560).

[0007] Further, the water-soluble acrylic resin is a self-crosslinking type acrylic resin with a solid content of 20-40%.

[0008] Further, the amount ratio of graphene oxide, water-ethanol mixed solvent and γ-aminopropyl triethoxysilane is 1g:200mL:5g, and the volume ratio of the water-ethanol mixed solvent is 1:1.

[0009] The present application has the following advantages: through silane modification, graphene can be stably dispersed in the passivation liquid in the form of nanosheet layers, and is arranged in parallel to the metal surface during film forming, forming a "labyrinth effect", greatly extending the diffusion path of the corrosion medium. The silane end group on the modified graphene surface can form a firm chemical bond (Si-O-Me) with the hydroxyl group on the metal surface and the zirconium and titanium hydrolysis products in the passivation liquid, solving the problem of weak adhesion between graphene and the substrate. The physical barrier effect of graphene and the chemical passivation effect of the zirconium and titanium nano conversion film are synergistic, and the corrosion resistance of the obtained nano composite film is far superior to that of traditional phosphorus-free conversion films, and the whole process is free of phosphorus, chromium and nickel, green and environmentally friendly. The present application is suitable for various construction processes such as immersion and spraying. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0011] Embodiment 1: Preparation of silane modified graphene oxide dispersion liquid, specifically including the following steps: In a 500mL three-necked flask equipped with a stirrer and a reflux condenser, 200mL of water-ethanol mixed solvent with a volume ratio of 1:1 was added, and then 1.0g of graphene oxide powder was added. The mixture was ultrasonically dispersed (power 600W) at room temperature for 1 hour to obtain a uniform graphene oxide dispersion liquid. 5.0g of γ-aminopropyl triethoxysilane (KH-550) was added, and the pH of the system was adjusted to 4-5 with acetic acid. Then the mixture was heated to 70°C, and refluxed for 6 hours under stirring. After the reaction was completed, the temperature was cooled to room temperature to obtain a silane modified graphene oxide dispersion liquid with a concentration of about 0.5%.

[0012] Embodiment 2: Preparation method of phosphorus-free nano passivation liquid containing modified graphene, specifically including the following steps: A beaker was taken, 800mL of deionized water was added, and the following components were sequentially added and stirred until completely dissolved: 200g of the silane modified graphene oxide dispersion liquid prepared in Embodiment 1 (providing 1.0g of graphene oxide), fluorozirconic acid (providing 0.5g of Zr), fluorotitanic acid (providing 0.5g of Ti), and 0.5g of sodium citrate. 1.0g), fluorotitanic acid (providing 0.5g of Ti), and 0.5g of sodium citrate. 20.5g), water-soluble acrylic resin (solid content 30%, added amount equivalent to 3g on dry basis), KH-560 silane coupling agent 3g, adjust pH to 4.0 with dilute nitric acid, and finally dilute to 1 liter with deionized water, stir until uniform, to obtain the passivation solution.

[0013] Example 3, preparation method of phosphorus-free nano passivation solution containing modified graphene, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage of each liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (provides graphene oxide 0.3g), fluorozirconic acid (provides 0.5g), fluorotitanic acid (provides 0.1g), water-soluble acrylic resin (dry basis 10g), KH-550 silane coupling agent 5g, and the pH value is adjusted to 3.5.

[0014] Example 4, preparation method of phosphorus-free nano passivation solution containing modified graphene, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage of each liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (provides graphene oxide 0.4g), fluorozirconic acid (provides 2.0g), fluorotitanic acid (provides 1.0g), water-soluble acrylic resin (dry basis 1g), KH-550 silane coupling agent 1g, and the pH value is adjusted to 4.5.

[0015] Example 5, preparation method of phosphorus-free nano passivation solution containing modified graphene, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage of each liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (provides graphene oxide 0.5g), fluorozirconic acid (provides 1.5g), fluorotitanic acid (provides 0.2g), water-soluble acrylic resin (dry basis 5g), KH-550 silane coupling agent 2g, and the pH value is adjusted to 3.8.

[0016] Example 6, preparation method of phosphorus-free nano passivation solution containing modified graphene, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage of each liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (provides graphene oxide 0.2g), fluorozirconic acid (provides 0.8g), fluorotitanic acid (provides 0.8g), water-soluble acrylic resin (dry basis 8g), KH-560 silane coupling agent 4g, and the pH value is adjusted to 4.2.

[0017] Example 7, preparation method of phosphorus-free nano passivation solution containing modified graphene, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage per liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (providing graphene oxide 0.5 g), fluorozirconic acid (providing 1.2 g), fluorotitanic acid (providing 0.1 g), ammonium molybdate 0.5 g, water-soluble acrylic resin (dry basis 5 g), KH-550 silane coupling agent 2 g, and the pH value is adjusted to 4.0-4.5 with ammonia water.

[0018] Example 8, preparation method of modified graphene-containing phosphorus-free nano passivation solution, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage per liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (providing graphene oxide 0.1 g), fluorozirconic acid (providing 1.8 g), fluorotitanic acid (providing 0.6 g), water-soluble acrylic resin (dry basis 3 g), KH-560 silane coupling agent 4 g, and the pH value is adjusted to 3.6-4.0 with nitric acid.

[0019] Example 9, preparation method of modified graphene-containing phosphorus-free nano passivation solution, specifically comprising the following steps: The preparation method is the same as that of Example 2, and the raw material usage per liter of passivation solution is adjusted as follows: silane-modified graphene oxide dispersion (providing graphene oxide 0.7 g), fluorozirconic acid (providing 0.9 g), fluorotitanic acid (providing 0.3 g), benzotriazole (BTA) 0.8 g, water-soluble phenylpropyl resin 8 g, vinyltrimethoxysilane 1.5 g, and the pH value is adjusted to 4.0-4.5 with citric acid.

[0020] Comparative Example 1: The only difference between this comparative example and Example 2 is that unmodified graphene oxide dispersion is used instead of silane-modified graphene oxide dispersion, and the rest of the components and usage are exactly the same.

[0021] Comparative Example 2: The only difference between this comparative example and Example 2 is that no graphene component is added, and the rest of the components and usage are exactly the same.

[0022] Performance test Aluminum alloy sample: A certain factory's aluminum alloy sample with a size of 100x50x3mm and a material of aluminum alloy 6061 is used.

[0023] Aluminum alloy sample production process: water washing → degreasing → water washing → film plating → electrophoretic coating → water washing → air drying at room temperature; Specific application method: after the aluminum alloy sample plate is washed with water, it is placed in the oil removal agent to remove grease, and the surface of the sample plate is not hung with water droplets as the oil removal qualified standard. After washing with water again, it is placed in different phosphorus-free nano composite passivation solutions for film plating, the film plating time is 10 minutes, then electrocoating (cathode electrocoating paint, curing condition 170℃ / 20min) is carried out, after ending, it is washed with water again and dried at room temperature.

[0024] The adhesion test, neutral salt spray resistance test and cyclic corrosion resistance experiment are carried out on the aluminum alloy sample plate.

[0025] Cross-hatch adhesion test (GB / T9286-2021); Neutral salt spray test (GB / T10125-2021); Cyclic corrosion resistance test (GMW14872-2021); Table 1 is the test result of the corrosion resistance of the aluminum alloy sample plate.

[0026] Table 1 Sample Substrate Scratch adhesion (grade) Neutral salt spray test (1000 h) Cyclic corrosion test (1000 h) Example 2 Aluminum alloy panel 0 No significant change No significant change Example 3 Aluminum alloy panel 0 No significant change No significant change Example 4 Aluminum alloy panel 0 No significant change No significant change Example 5 Aluminum alloy panel 0 No significant change No significant change Example 6 Aluminum alloy panel 0 No significant change No significant change Example 7 Aluminum alloy panel 0 No significant change No significant change Example 8 Aluminum alloy panel 1 Slight corrosion Slight corrosion Example 9 Aluminum alloy panel 0 No significant change No significant change Comparative Example 1 Aluminum alloy panel 1 Slight corrosion Slight corrosion Comparative Example 2 Aluminum alloy panel 0 Slight corrosion Slight corrosion Commercially available non-phosphorus agent Aluminum alloy panel 1~2 Corrosion Corrosion From table 1, it can be seen that the adhesion and corrosion resistance of the sample plate treated by the passivation solution prepared by the application are significantly better than those of the comparative examples and the commercially available phosphorus-free product, which reflects the significant enhancement effect of the modified graphene.

[0027] The above content is only an example and description of the concept of the application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, as long as they do not deviate from the concept of the application or exceed the scope defined by the present claims, which shall belong to the protection scope of the application.

Claims

1. A phosphorus-free nanopassivation solution containing modified graphene, characterized in that: It includes the following components in parts by weight: 20-200 parts of silane-modified graphene oxide dispersion 0.5-2.0 portions 0.1-1.0 parts, 1-10 parts of water-soluble acrylic resin, 1-5 parts of silane coupling agent, and the balance being deionized water, wherein the pH value of the passivation solution is 3.5-4.

5.

2. The phosphorus-free nanopassivation solution containing modified graphene according to claim 1, characterized in that: The silane-modified graphene oxide dispersion was prepared by the following method: graphene oxide was dispersed in a water-ethanol mixed solvent, a silane coupling agent was added, and the mixture was heated under acidic conditions and refluxed to obtain the silane-modified graphene oxide dispersion.

3. The phosphorus-free nanopassivation solution containing modified graphene according to claim 2, characterized in that: The ratio of graphene oxide, water-ethanol mixed solvent, and γ-aminopropyltriethoxysilane is 1 g: 200 mL: 5 g, and the volume ratio of the water-ethanol mixed solvent is 1:

1.

4. The phosphorus-free nanopassivation solution containing modified graphene according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

5. The phosphorus-free nanopassivation solution containing modified graphene according to claim 1, characterized in that: The water-soluble acrylic resin is a self-crosslinking acrylic resin with a solid content of 20-40%.

6. A method for preparing a phosphorus-free nanopassivation solution containing modified graphene as described in claim 1, characterized in that: Each component is dissolved or dispersed in deionized water in sequence, and the pH is finally adjusted to 3.5-4.5 to obtain a passivation solution.

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