Screw rod with corrosion-resistant film layer and preparation method of screw rod

Abstract

The invention discloses a screw with a corrosion-resistant film layer and a preparation method of the screw. The screw with the corrosion-resistant film layer comprises an iron-based screw body and the corrosion-resistant film layer wrapping the surface of the iron-based screw body. The corrosion-resistant film layer is prepared from the following components in percentage by weight: 8 to 15 percent of phytic acid-copper complex, 5 to 12 percent of molybdate radical intercalation corrosion inhibitor, 3 to 7 percent of chestnut tannin, 0.5 to 1 percent of silane coupling agent, 0.2 to 0.5 percent of tea saponin, 2 to 5 percent of pH buffering agent, 0.5 to 1 percent of sodium polyacrylate, 1.5 to 3.5 percent of nano SiO2 dispersion liquid and the balance of water. And the corrosion-resistant film layer improves the corrosion resistance of the screw rod, and is good in film-forming property and high in adhesive force.

Description

TECHNICAL FIELD

[0001] The application relates to a screw with a corrosion-resistant film layer and a preparation method thereof, and belongs to the technical field of fastener processing. BACKGROUND

[0002] In the field of mechanical manufacturing and assembly, the corrosion resistance of screws and other fasteners directly affects the service life of equipment. The screws are usually made of iron-based materials, and the corrosion resistance is mainly realized through zinc electroplating, Dacromet coating, traditional blackening or phosphating treatment. However, the corrosion resistance effect after zinc electroplating is not ideal, the Dacromet coating contains carcinogenic hexavalent chromium, the film formed by traditional blackening treatment is loose and porous, and the film layer formed by phosphating treatment is relatively brittle and prone to falling off. SUMMARY

[0003] The application aims to provide a screw with a corrosion-resistant film layer and a preparation method thereof, which has excellent corrosion resistance and good film-forming property and high adhesion.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows: A screw with a corrosion-resistant film layer, comprising an iron-based screw and a corrosion-resistant film layer coated on the surface of the iron-based screw; the raw material of the corrosion-resistant film layer comprises the following components: 8-15wt% of a phytic acid-copper complex, 5-12wt% of a molybdate intercalation corrosion inhibitor, 3-7wt% of chestnut tannin, 0.5-1wt% of a silane coupling agent, 0.2-0.5wt% of tea saponin, 2-5wt% of a pH buffer, 0.5-1wt% of sodium polyacrylate, 1.5-3.5wt% of a nano-SiO2 dispersion liquid, and the balance being water.

[0005] Preferably, the preparation method of the phytic acid-copper complex is that phytic acid and copper powder are mixed in a molar ratio of (2-4):1, and then reacted at 45-65 DEG C for 1-3h.

[0006] Preferably, the preparation method of the molybdate intercalation corrosion inhibitor comprises the following steps: S1, under nitrogen protection, a solution containing Ca 2+ and Al 3+ ions is added dropwise into a sodium nitrate solution, the pH is adjusted to 9-10, and after secondary aging, centrifugation, washing and vacuum drying, calcium-aluminum layered double hydroxide is obtained; S2, the calcium-aluminum layered double hydroxide is dispersed into a Na2MoO4 solution, heated and stirred for crystallization treatment, and after suction filtration, washing and drying, molybdate intercalation calcium-aluminum layered double hydroxide is obtained; S3, the molybdate intercalation calcium-aluminum layered double hydroxide is placed in an alcohol solution containing KH-550, and after ultrasonic treatment, heating and stirring are performed, and then vacuum drying treatment is performed to obtain a modified molybdate intercalation calcium-aluminum layered double hydroxide, which is mixed and stirred with a preheated polyurethane-acrylate hybrid emulsion.

[0007] Preferably, in step S1, the solution containing Ca 2+ , Al 3+ ions, the molar ratio of Ca 2+ to Al 3+ is (2.7-3):1; The concentration of NO 3- in the sodium nitrate solution is 2.5-3 mol / L; The volume ratio of the solution containing Ca 2+ , Al 3+ ions to the sodium nitrate solution is 1:(2.6-2.8); When dropping, the temperature condition of the sodium nitrate solution is 50-55℃.

[0008] Preferably, in step S1, the method of secondary aging is to first incubate at 60-65℃ for 23-25h, and then incubate at 105-110℃ for 40-45h; The conditions for vacuum drying are 75-85℃ for 10-15h.

[0009] Preferably, in step S2, the concentration of the Na2MoO4 solution is 0.4-0.5mol / L; The solid-liquid ratio of the calcium-aluminum layered double hydroxide to the Na2MoO4 solution is 1g:(40-60)mL; The conditions for heating and stirring are 65-75℃ for 15-20h; The conditions for crystallization are microwave irradiation power of 200-500W for 20-30min; The drying conditions are 55-75℃ for 15-20h.

[0010] Preferably, in step S3, the content of KH-550 in the alcohol solution containing KH-550 is 0.5-1.2wt%; The mass ratio of the molybdate intercalation calcium-aluminum layered double hydroxide to the alcohol solution containing KH-550 is 1:(3-5); The conditions for heating and stirring are 55-65℃ for 1-3h; The conditions for vacuum drying are 60-80℃ for 3-5h.

[0011] Preferably, in step S3, the preheated temperature of the polyurethane-acrylate hybrid emulsion is 40-60℃; The mass ratio of the modified molybdate intercalation calcium-aluminum layered double hydroxide to the polyurethane-acrylate hybrid emulsion is 1: (3.5-5).

[0012] The preparation method of the screw with the corrosion-resistant film layer is as follows: after oil removal and sand blasting treatment of the iron-based screw, oxalic acid activation is performed, and then the screw is immersed in a treatment liquid prepared from raw materials of the corrosion-resistant film layer after water washing, and the immersion is repeated for multiple times, and then the screw is drained, air-oxidized, and subjected to alkali neutralization and water washing, and then heat curing is performed.

[0013] Preferably, the preparation process of the treatment liquid is as follows: deionized water, a pH buffer, polyacrylonitrile sodium, and a nano-SiO2 dispersion liquid are added into a reaction kettle, and then a molybdate intercalation corrosion inhibitor is slowly added at a rotation speed of 200 rpm, and after the addition is completed, the stirring is continued for 10-20 min, and then phytic acid-copper complex, chestnut tannin, and tea saponin are added, and finally a silane coupling agent is added, and the treatment liquid is obtained after ultrasonic treatment.

[0014] The present application has the following beneficial effects: The iron-based screw surface exposed fresh Fe after oxalic acid activation 0 Active sites, which are chelated with phytic acid under the action of Cu 2+ To form a dense passivation film, which can effectively prevent corrosion; at the same time, when local corrosion occurs, the molybdate intercalation corrosion inhibitor releases molybdate ions through the slow-release characteristics of the layered double hydroxide, and the molybdate ions combine with iron ions to form insoluble substances, preventing further corrosion from occurring. As a natural polyphenolic substance, chestnut tannin can fill the micropores of the passivation film, enhance its density, and inhibit the rusting reaction; the nanoparticles in the nano-SiO2 dispersion liquid can fill the gaps in the film layer, increase the hardness and wear resistance of the film layer, and block the penetration of corrosive ions; and the combination of the polyurethane-acrylate hybrid emulsion, the silane coupling agent, and the tea saponin effectively improves the film-forming property and the adhesion of the film layer. DETAILED DESCRIPTION

[0015] In the following examples and comparative examples, the preparation method of the phytic acid-copper complex is as follows: phytic acid and copper powder are mixed in a molar ratio of 2:1, and then reacted at 50℃ for 2h.

[0016] The preparation method of the molybdate intercalation corrosion inhibitor includes the following steps: under nitrogen protection, calcium nitrate tetrahydrate and aluminum nitrate nonahydrate are dissolved in deionized water in a molar ratio of 3:1, and then the solution is added dropwise to a sodium nitrate solution (NO 2+ , Al 3+ The molar ratio of the calcium nitrate tetrahydrate and the aluminum nitrate nonahydrate is 3:1, and the solution is added dropwise to a sodium nitrate solution (NO 3-The calcium-aluminum layered double hydroxide was dispersed into Na2MoO4 solution (0.5 mol / L) at a solid-liquid ratio of 1 g:50 mL, stirred at 70°C for 18 h, and then subjected to microwave irradiation at a power of 300 W for 30 min. After filtration, washing, and drying (60°C, 15 h), the molybdate intercalated calcium-aluminum layered double hydroxide was obtained.

[0017] The calcium-aluminum layered double hydroxide was dispersed into Na2MoO4 solution (0.5 mol / L) at a solid-liquid ratio of 1 g:50 mL, stirred at 70°C for 18 h, and then subjected to microwave irradiation at a power of 300 W for 30 min. After filtration, washing, and drying (60°C, 15 h), the molybdate intercalated calcium-aluminum layered double hydroxide was obtained.

[0018] The molybdate intercalated calcium-aluminum layered double hydroxide was placed in an alcohol solution containing KH-550 (the content of KH-550 was 1 wt%) at a mass ratio of 1:3, ultrasonically treated, stirred at 60°C for 2 h, and then vacuum dried at 70°C for 5 h to obtain the modified molybdate intercalated calcium-aluminum layered double hydroxide. The modified molybdate intercalated calcium-aluminum layered double hydroxide was mixed with a polyurethane-acrylate hybrid emulsion at a mass ratio of 1:4 to obtain the treatment solution.

[0019] Example 1: The raw materials of the treatment solution included the following components in the following mass contents: 12 wt% phytic acid-copper complex, 8 wt% molybdate intercalated corrosion inhibitor, 5 wt% chestnut tannin, 0.5 wt% silane coupling agent (KH550), 0.5 wt% tea saponin, 3 wt% pH buffer (citric acid), 0.5 wt% polyacrylic acid sodium, 2 wt% nano-SiO2 dispersion (the content of SiO2 was 25 wt%), and water (the balance).

[0020] Deionized water, citric acid, polyacrylamide sodium, and nano-SiO2 dispersion were added to a reaction kettle, and the molybdate intercalated corrosion inhibitor was slowly added at a rotation speed of 200 rpm. After the addition was completed, the mixture was continuously stirred for 10 min, and then the phytic acid-copper complex, chestnut tannin, and tea saponin were added. Finally, KH550 was added, and the mixture was ultrasonically treated for 20 min to obtain the treatment solution.

[0021] Then, the iron-based screw was subjected to oil removal and sand blasting, activated with oxalic acid, washed with water, and then immersed in the above treatment solution. After repeated immersion for 3 times (each time for 10 min), the screw was drained, air oxidized, neutralized with alkali, washed with water, and then heat cured (130°C, 15 min) to obtain the treated iron-based screw.

[0022] Comparative Example 1: The same as Example 1, except that the phytic acid-copper complex was not added to the treatment solution.

[0023] Comparative Example 2: The same as Example 1, except that the molybdate intercalated corrosion inhibitor was not added to the treatment solution.

[0024] Comparative Example 3: substantially the same as Example 1, except that no chestnut tannin was added to the treatment solution.

[0025] The treated bolts in Example 1 and Comparative Example 3 were tested for performance, and the testing standards were as follows: salt spray resistance test: tested according to GJB715.1-89 standard, and the time (h) for the appearance of the substrate was recorded; acid corrosion resistance: 20% acetic acid solution was used for dripping, and the time (min) for the appearance of the substrate was recorded; 5% oxalic acid solution was used for dripping, and the time (min) for the appearance of the substrate was recorded; rust resistance: 3% CuSO4·5H2O solution was used for dripping, and the time (s) for the appearance of rust was recorded. The test results are shown in Table 1.

[0026] Table 1

[0027] As can be seen from the data in Table 1, the treated bolt in Example 1 has the best corrosion resistance, which is due to the presence of the passivation film and the corrosion inhibitor, which improves the corrosion resistance, and the enhanced film density due to the filling of the pores of the passivation film by the chestnut tannin, as well as the combination of the phytic acid-copper complex and the molybdate intercalation corrosion inhibitor, which improves the corrosion resistance.

[0028] The above only describes the preferred embodiments of the present patent, and it should be noted that for those skilled in the art, without departing from the principles of the present patent, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present patent.

Claims

1. A screw with a corrosion-resistant film layer, characterized in that, It includes an iron-based screw and a corrosion-resistant film coating the surface of the iron-based screw; the raw materials of the corrosion-resistant film include the following components: 8-15wt% phytic acid-copper complex, 5-12wt% molybdate intercalation corrosion inhibitor, 3-7wt% chestnut tannin, 0.5-1wt% silane coupling agent, 0.2-0.5wt% tea saponin, 2-5wt% pH buffer, 0.5-1wt% sodium polyacrylate, 1.5-3.5wt% nano-SiO2 dispersion, and the balance being water.

2. The screw with a corrosion-resistant film layer according to claim 1, characterized in that, The preparation method of phytic acid-copper complex is to mix phytic acid and copper powder in a molar ratio of (2-4):1 and react them at 45-65℃ for 1-3 hours.

3. The screw with a corrosion-resistant film layer according to claim 1, characterized in that, The preparation method of molybdate intercalation corrosion inhibitor includes the following steps: S1, under nitrogen protection, containing Ca 2+ Al 3+ The solution of ions was added dropwise to sodium nitrate solution, the pH was adjusted to 9-10, and after two aging processes, it was centrifuged, washed, and vacuum dried to obtain calcium-aluminum layered double hydroxide. S2. The calcium-aluminum layered double hydroxide was dispersed in Na2MoO4 solution, heated and stirred, crystallized, filtered, washed and dried to obtain molybdate-intercalated calcium-aluminum layered double hydroxide. S3. Place the molybdate-intercalated calcium-aluminum layered double hydroxide in an alcohol solution containing KH-550, sonicate it, heat and stir it, and then vacuum dry it to obtain the modified molybdate-intercalated calcium-aluminum layered double hydroxide. Then mix and stir it with the preheated polyurethane-acrylate hybrid emulsion.

4. The screw with a corrosion-resistant film layer according to claim 3, characterized in that, In step S1, Ca is included. 2+ Al 3+ In a solution of ions, Ca 2+ With Al 3+ The molar ratio is (2.7-3):1; In sodium nitrate solution, NO 3- The concentration is 2.5-3 mol / L; Contains Ca 2+ Al 3+ The volume ratio of the ion solution to the sodium nitrate solution is 1:(2.6-2.8); When adding sodium nitrate dropwise, the temperature of the sodium nitrate solution should be 50-55℃.

5. The screw with a corrosion-resistant film layer according to claim 3, characterized in that, In step S1, the secondary aging method is as follows: first, keep warm at 60-65℃ for 23-25 ​​hours, and then keep warm at 105-110℃ for 40-45 hours; The conditions for vacuum drying are: 75-85℃, 10-15h.

6. The screw with a corrosion-resistant film layer according to claim 3, characterized in that, In step S2, the concentration of the Na2MoO4 solution is 0.4-0.5 mol / L; The solid-liquid ratio of calcium-aluminum layered double hydroxide to Na2MoO4 solution is 1g:(40-60)mL; The heating and stirring conditions are: 65-75℃, 15-20h; The crystallization conditions are: microwave radiation power 200-500W, 20-30min; The drying conditions are: 55-75℃ for 15-20 hours.

7. The screw with a corrosion-resistant film layer according to claim 3, characterized in that, In step S3, the KH-550 content in the alcohol solution containing KH-550 is 0.5-1.2 wt%. The mass ratio of molybdate intercalated calcium aluminum layered double hydroxide to alcohol solution containing KH-550 is 1:(3-5); The heating and stirring conditions are: 55-65℃, 1-3h; The conditions for vacuum drying are: 60-80℃, 3-5h.

8. The screw with a corrosion-resistant film layer according to claim 3, characterized in that, In step S3, the temperature of the polyurethane-acrylate hybrid emulsion after preheating is 40-60℃; The mass ratio of the modified molybdate intercalated calcium-aluminum layered double hydroxide to the polyurethane-acrylate hybrid emulsion is 1:(3.5-5).

9. A method for preparing a screw with a corrosion-resistant film layer according to any one of claims 1-8, characterized in that, The process involves degreasing and sandblasting the iron-based screw, followed by activation with oxalic acid, washing with water, immersing it in a treatment solution prepared from corrosion-resistant film material, repeatedly immersing it multiple times, draining it, oxidizing it in air, neutralizing it with alkali, washing it with water, and then heat curing it.

10. The method for preparing a screw with a corrosion-resistant film layer according to claim 9, characterized in that, The preparation process of the treatment solution is as follows: Deionized water, pH buffer, sodium polyacrylamide and nano-SiO2 dispersion are added to the reactor. Molybdate intercalation corrosion inhibitor is slowly added at 200 rpm. After the addition is completed, stirring is continued for 10-20 min. Then, phytic acid-copper complex, chestnut tannin and tea saponin are added. Finally, silane coupling agent is added. After ultrasonic treatment, the treatment solution is obtained.

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