Treatment method of corrosion-resistant hot-dip galvanized workpiece

Abstract

The invention discloses a treatment method of a corrosion-resistant hot galvanizing workpiece, and belongs to the technical field of hot galvanizing. The treatment method comprises the following steps: cleaning and drying the surface of the hot-dip galvanized component, then uniformly spraying an anti-corrosion coating on the surface of the hot-dip galvanized component, and obtaining an anti-corrosion hot-dip galvanized workpiece after the coating is cured, the anticorrosive paint comprises the following components in parts by weight: 30-50 parts of modified epoxy resin, 1-2 parts of an anti-freezing agent, 1-3 parts of a defoaming agent, 10-20 parts of modified nano silicon dioxide, 1-3 parts of a dispersing agent, 3-5 parts of a curing agent and 15-20 parts of acetone. The anti-corrosion coating has good comprehensive performance, the corrosion resistance of a hot-dip galvanized workpiece is remarkably improved, the corrosion speed of the hot-dip galvanized workpiece in a severe environment is delayed, and therefore the service life of the hot-dip galvanized workpiece is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip galvanizing, and in particular to a method for processing a corrosion-resistant hot-dip galvanized workpiece. Background Art

[0002] The entire process of hot-dip galvanizing requires placing the pretreated steel into molten zinc liquid at a temperature of 445-460°C. Complex physical and chemical changes occur during the entire process. The solid steel and the zinc liquid undergo infiltration, diffusion, and dissolution. Finally, a galvanized layer is formed on the surface of the substrate, of which the inner layer is an iron-zinc alloy and the outer layer is a pure zinc layer. The hot-dip galvanized layer can better protect the substrate and slow down the corrosion process.

[0003] The hot-dip galvanizing process primarily involves four steps: pre-galvanizing surface treatment, flux treatment, hot-dip plating, and post-galvanizing treatment. The process is as follows: alkaline degreasing – pickling for rust removal – water washing for impurity removal – flux treatment – drying – hot-dip plating – post-galvanizing treatment – and finished product. Pre-galvanizing surface treatment aims to remove oil, oxides, and other impurities from the steel surface, ensuring uniform adhesion of the subsequent zinc solution. Flux treatment involves coating the workpiece surface with a flux (such as zinc chloride or ammonium chloride) to further improve the wettability of the steel substrate with the zinc solution. Hot-dip plating involves immersing the workpiece in molten zinc, allowing the zinc solution to react with the substrate to form a zinc coating. Post-galvanizing treatment, including passivation, oiling, or other surface treatments, enhances the corrosion resistance and appearance of the zinc coating.

[0004] Chinese patent document CN109705693A discloses a method for anticorrosion of hot-dip galvanized structures. The key technical aspects of the method are: S1: treating the surface of a metal component through a hot-dip galvanizing process to produce a hot-dip galvanized component; S2: uniformly coating the surface of the hot-dip galvanized component with an anticorrosive coating, which is then cured. The anticorrosive coating comprises the following components: a water-based epoxy resin emulsion, a curing agent, a tackifier, an anticorrosive filler, and an anti-rust pigment. This invention involves applying an anticorrosive coating to the hot-dip galvanized metal component after the metal component has been hot-dip galvanized to form a galvanized layer. This coating enhances the corrosion protection of the metal component. Even if the galvanized layer becomes rough due to excessive iron content in the zinc solution, the coating can smoothen the surface of the coated component, further enhancing the corrosion protection. This method eliminates the need for strict control of the zinc solution's purity and improves the corrosion protection of the hot-dip galvanized component. However, the hot-dip galvanized surface is typically relatively smooth, and the anticorrosive coating has poor adhesion to the hot-dip galvanized surface, which can affect the long-term stability of the anticorrosive coating. Summary of the Invention

[0005] The main purpose of the present invention is to propose a method for treating corrosion-resistant hot-dip galvanized workpieces, by coating an anti-corrosion coating on the surface of the hot-dip galvanized workpiece. The anti-corrosion coating has good comprehensive performance and good long-term stability, and can delay the corrosion rate of the workpiece in harsh environments, thereby greatly improving the service life of the hot-dip galvanized workpiece.

[0006] To achieve the above object, the present invention provides a method for treating a corrosion-resistant hot-dip galvanized workpiece, comprising the following steps: Clean and dry the surface of the hot-dip galvanized component, then evenly spray anti-corrosion paint on the surface of the hot-dip galvanized component, and obtain a corrosion-resistant hot-dip galvanized workpiece after the paint is cured.

[0007] Preferably, the anti-corrosion coating comprises the following components in parts by weight: 30-50 parts of modified epoxy resin, 1-2 parts of antifreeze agent, 1-3 parts of defoaming agent, 10-20 parts of modified nano-silica, 1-3 parts of dispersant, 3-5 parts of curing agent, 15-20 parts of acetone.

[0008] Preferably, the preparation method of the modified epoxy resin is as follows: Hexamethylene diisocyanate and terminal hydroxyl perfluoropolyether are mixed evenly and heated to react to obtain compound 1. Under a nitrogen atmosphere, compound 1 and epoxy resin are mixed evenly and heated to react for a period of time, and then stannous octoate is added to continue the reaction to obtain a modified epoxy resin.

[0009] Preferably, the mass ratio of hexamethylene diisocyanate, hydroxyl-terminated perfluoropolyether, and epoxy resin is 2-4:1:10-15.

[0010] Preferably, the antifreeze agent is ethylene glycol or propylene glycol.

[0011] Preferably, the defoaming agent is at least one of a phosphate hydrophobic defoaming agent, polysiloxane, and an organic alcohol compound.

[0012] Preferably, the dispersant is at least one of sodium tripolyphosphate, sodium hexametaphosphate, triethylhexyl phosphate, sodium lauryl sulfate, and methyl amyl alcohol.

[0013] Preferably, the preparation method of the modified nano-silica is as follows: The method comprises the following steps: dispersing nano-silica in a solvent, adding an aminosilane coupling agent, and heating to react to obtain amino-modified nano-silica; adding the amino-modified nano-silica to N,N-dimethylformamide, adding an aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-imidazole acrylic acid, adjusting the pH value to be weakly acidic, heating to react, and collecting a solid; and dissolving dodecenylsuccinic acid in toluene, adding the solid and ammonium persulfate, and heating to react to obtain the modified nano-silica.

[0014] Preferably, the mass ratio of the nano-silica and the aminosilane coupling agent is 15-25:3-5; the mass ratio of the amino-silica, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution, 4-imidazole acrylic acid, and dodecenylsuccinic acid is 10-20:100:5-8:6-10; and the concentration of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution is 10-30wt%.

[0015] The present invention also discloses a method for preparing the anti-corrosion coating, comprising the following steps: The raw materials are weighed according to the formula, and the modified epoxy resin, antifreeze agent, defoamer, modified nano-silica, dispersant, curing agent and acetone are mixed and stirred evenly to obtain the anti-corrosion coating.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention uses epoxy resin as a film-forming material, which can firmly adhere to the surface of the coated hot-dip galvanized workpiece, forming a tough hydrophobic protective film, effectively preventing the intrusion of corrosive media, ensuring that the coating can maintain good protective performance in various harsh environments, and extending the service life of the protected hot-dip galvanized workpiece; 2) By modifying the epoxy resin, the present invention can significantly improve its flexibility, effectively resisting cracking and flaking caused by thermal expansion and contraction or external forces. Furthermore, by introducing fluorine, the epoxy resin's yellowing resistance is improved, while also enhancing its weather resistance, chemical resistance, and hydrophobicity. This improves the epoxy resin's optical stability, reduces degradation caused by ultraviolet radiation, and enhances the coating's self-cleaning and anti-pollution capabilities. Furthermore, the large number of ether bonds in the perfluoropolyether can be adsorbed on the surface of hot-dip galvanized workpieces, improving the adhesion of the anti-corrosion coating to the surface. 3) Nano-silica has high hardness, excellent wear resistance, corrosion resistance and nano-size effect, which can make the structure of the coating very compact and increase the strength. The present invention improves the dispersibility of nano-silica in epoxy resin by modifying the nano-silica, which is beneficial to improving the wear resistance of the coating and effectively avoiding the phenomenon that the coating is prone to fine cracks when used for a long time in harsh environments. By grafting 4-imidazole acrylic acid on the nano-silica, the imidazole group in the 4-imidazole acrylic acid can form a stable chelate with zinc on the surface of the hot-dip galvanized workpiece, stably adsorbed on the surface of the hot-dip galvanized workpiece, inhibiting the reduction reaction at the cathode and effectively protecting the hot-dip galvanized workpiece. In addition, the dodecenylsuccinic acid can cover the surface of the workpiece to form a dense hydrophobic protective film, further reducing the corrosion rate of the workpiece. DETAILED DESCRIPTION

[0017] To avoid redundancy, the items used in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0018] The sources of some raw materials used in the present invention are as follows: Hydroxyl-terminated perfluoropolyether, molecular weight 500-10000, was purchased from Hubei Xinyuhong Biopharmaceutical Technology Co., Ltd.

[0019] Epoxy resin, brand E-44, was purchased from Hebei Jingxin Innovation Materials Co., Ltd.

[0020] Example 1

[0021] A method for preparing an anti-corrosion coating comprises the following steps: 400 g of modified epoxy resin, 14.6 g of propylene glycol, 15.3 g of tributyl phosphate, 149 g of modified nano-silica, 20.5 g of sodium hexametaphosphate, 40.8 g of polyamide curing agent 650, and 180 g of acetone were mixed and stirred uniformly to obtain the anti-corrosion coating.

[0022] The preparation method of the modified epoxy resin is as follows: 30 g of hexamethylene diisocyanate and 10 g of terminal hydroxyl perfluoropolyether were mixed evenly, heated at 85 ° C for 3 h, and the unreacted reactants were evaporated under reduced pressure to obtain compound 1. Under a nitrogen atmosphere, compound 1 and 125 g of epoxy resin were mixed evenly, heated at 110 ° C for 3 h, and then stannous octoate was added and the reaction was continued at this temperature for 1 h. The unreacted reactants were evaporated under reduced pressure to obtain a modified epoxy resin.

[0023] The preparation method of the modified nano-silica is as follows: 20 g of nano-silica was dispersed in 200 mL of 50 wt% ethanol aqueous solution, 4.2 g of KH-550 was added, and the mixture was heated at 50° C. for 3 h, filtered, and the solid was collected, washed, and dried to obtain amino-modified nano-silica; 18.3 g of amino-modified nano-silica was added to 200 mL of N,N-dimethylformamide, 100 g of 20 wt% 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution and 6.5 g of 4-imidazole acrylic acid were added, and the pH value was adjusted to 6. The mixture was heated at 70° C. for 4 h, and the solid was collected; 8.3 g of dodecenylsuccinic acid was dissolved in 200 mL of toluene, the solid and 0.8 g of ammonium persulfate were added, and the mixture was heated at 80° C. for 3 h. The solid was filtered, collected, washed, and dried to obtain the modified nano-silica.

[0024] Example 2

[0025] A method for preparing an anti-corrosion coating comprises the following steps: 300 g of modified epoxy resin, 10.3 g of propylene glycol, 10.5 g of tributyl phosphate, 100 g of modified nano-silica, 10.2 g of sodium hexametaphosphate, 30 g of polyamide curing agent 650, and 150 g of acetone were mixed and stirred uniformly to obtain the anti-corrosion coating.

[0026] The preparation method of the modified epoxy resin is as follows: 20 g of hexamethylene diisocyanate and 10 g of terminal hydroxyl perfluoropolyether were mixed evenly, heated at 85 ° C for 3 h, and the unreacted reactants were evaporated under reduced pressure to obtain compound 1. Under a nitrogen atmosphere, compound 1 and 100 g of epoxy resin were mixed evenly and heated at 110 ° C for 3 h. Stannous octoate was added and the reaction was continued at this temperature for 1 h. The unreacted reactants were evaporated under reduced pressure to obtain a modified epoxy resin.

[0027] The preparation method of the modified nano-silica is as follows: 15 g of nano-silica was dispersed in 200 mL of 50 wt% ethanol aqueous solution, 3 g of KH-550 was added, and the mixture was heated at 50° C. for 3 h, filtered, and the solid was collected, washed, and dried to obtain amino-modified nano-silica; 10.5 g of amino-modified nano-silica was added to 200 mL of N,N-dimethylformamide, 100 g of a 20 wt% aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 5.2 g of 4-imidazole acrylic acid were added, and the pH value was adjusted to 6. The mixture was heated at 70° C. for 4 h, and the solid was collected; 6 g of dodecenylsuccinic acid was dissolved in 200 mL of toluene, the solid and 0.6 g of ammonium persulfate were added, and the mixture was heated at 80° C. for 3 h. The solid was filtered, collected, washed, and dried to obtain the modified nano-silica.

[0028] Example 3

[0029] A method for preparing an anti-corrosion coating comprises the following steps: 500 g of modified epoxy resin, 20 g of propylene glycol, 30 g of tributyl phosphate, 200 g of modified nano-silica, 30 g of sodium hexametaphosphate, 50 g of polyamide curing agent 650, and 200 g of acetone were mixed and stirred uniformly to obtain the anti-corrosion coating.

[0030] The preparation method of the modified epoxy resin is as follows: 30 g of hexamethylene diisocyanate and 10 g of terminal hydroxyl perfluoropolyether were mixed evenly, heated at 85 ° C for 3 h, and the unreacted reactants were evaporated under reduced pressure to obtain compound 1. Under a nitrogen atmosphere, compound 1 and 150 g of epoxy resin were mixed evenly, heated at 110 ° C for 3 h, and then stannous octoate was added and the reaction was continued at this temperature for 1 h. The unreacted reactants were evaporated under reduced pressure to obtain a modified epoxy resin.

[0031] The preparation method of the modified nano-silica is as follows: 25 g of nano-silica was dispersed in 200 mL of 50 wt% ethanol aqueous solution, 5 g of KH-550 was added, and the mixture was heated at 50° C. for 3 h, filtered, and the solid was collected, washed, and dried to obtain amino-modified nano-silica; 20 g of amino-modified nano-silica was added to 200 mL of N,N-dimethylformamide, 100 g of 20 wt% 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution and 5 g of 4-imidazole acrylic acid were added, and the pH value was adjusted to 6. The mixture was heated at 70° C. for 4 h, and the solid was collected; 10 g of dodecenylsuccinic acid was dissolved in 200 mL of toluene, the solid and 1 g of ammonium persulfate were added, and the mixture was heated at 80° C. for 3 h. The solid was filtered, collected, washed, and dried to obtain the modified nano-silica.

[0032] Comparative Example 1 A method for preparing an anti-corrosion coating is similar to that of Example 1, except that the epoxy resin is not modified, and specifically comprises the following steps: 400 g of epoxy resin, 14.6 g of propylene glycol, 15.3 g of tributyl phosphate, 149 g of modified nano-silica, 20.5 g of sodium hexametaphosphate, 40.8 g of polyamide curing agent 650, and 180 g of acetone were mixed and stirred uniformly to obtain the anti-corrosion coating.

[0033] The preparation method of the modified nano-silica is as follows: 20 g of nano-silica was dispersed in 200 mL of 50 wt% ethanol aqueous solution, 4.2 g of KH-550 was added, and the mixture was heated at 50° C. for 3 h, filtered, and the solid was collected, washed, and dried to obtain amino-modified nano-silica; 18.3 g of amino-modified nano-silica was added to 200 mL of N,N-dimethylformamide, 100 g of 20 wt% 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution and 6.5 g of 4-imidazole acrylic acid were added, and the pH value was adjusted to 6. The mixture was heated at 70° C. for 4 h, and the solid was collected; 8.3 g of dodecenylsuccinic acid was dissolved in 200 mL of toluene, the solid and 0.8 g of ammonium persulfate were added, and the mixture was heated at 80° C. for 3 h. The solid was filtered, collected, washed, and dried to obtain the modified nano-silica.

[0034] Comparative Example 2 A method for preparing an anti-corrosion coating is similar to that of Example 1, except that the nano-silica is not modified, and specifically comprises the following steps: 400 g of modified epoxy resin, 14.6 g of propylene glycol, 15.3 g of tributyl phosphate, 149 g of nano-silicon dioxide, 20.5 g of sodium hexametaphosphate, 40.8 g of polyamide curing agent 650, and 180 g of acetone were mixed and stirred uniformly to obtain the anti-corrosion coating.

[0035] The preparation method of the modified epoxy resin is as follows: 30 g of hexamethylene diisocyanate and 10 g of terminal hydroxyl perfluoropolyether were mixed evenly, heated at 85 ° C for 3 h, and the unreacted reactants were evaporated under reduced pressure to obtain compound 1. Under a nitrogen atmosphere, compound 1 and 125 g of epoxy resin were mixed evenly, heated at 110 ° C for 3 h, and then stannous octoate was added and the reaction was continued at this temperature for 1 h. The unreacted reactants were evaporated under reduced pressure to obtain a modified epoxy resin.

[0036] Performance Testing The surface of the hot-dip galvanized component was cleaned and dried, and then the anti-corrosion coatings prepared in Examples 1-3 and Comparative Examples 1-2 were evenly sprayed on the surface of the hot-dip galvanized component (three hot-dip galvanized plates were sprayed for each Example or Comparative Example, and the test results were averaged). The spraying thickness was uniformly 200 μm, and the coating was cured at 25°C for 7 days. The resulting coating was then tested.

[0037] Wear resistance test: Refer to GB / T1768-2006 "Paints and varnishes - Determination of wear resistance - Rotating rubber grinding wheel method" Adhesion test: refer to GB / T5210-2006 "Paints and varnishes adhesion test by pull-off method"; Corrosion resistance test: refer to GB / T31588.1-2015 "Paints and varnishes - Determination of resistance to cyclic corrosion environments - Part 1: Wet (salt spray) / dry / humid"; Water contact angle test: using PZ-200SD contact angle meter; Anti-ultraviolet aging test: Place the sample in an ultraviolet wavelength of 313nm and an irradiance of 0.54W / m 2 The UV aging box was used to observe the time when the sample turned yellow to judge its UV resistance. The test results are shown in Table 1: Table 1 Anticorrosion coating performance test results

[0038] It can be seen from the experimental results in Table 1 that the anti-corrosion coating prepared by the present invention has good wear resistance, adhesion, corrosion resistance, water resistance and UV aging resistance, and delays the corrosion rate of the hot-dip galvanized workpiece in harsh environments, thereby greatly improving the service life of the hot-dip galvanized workpiece.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. A method for processing a corrosion-resistant hot-dip galvanized workpiece, characterized in that: The processing method comprises the following steps: Clean and dry the surface of the hot-dip galvanized component, then evenly spray anti-corrosion paint on the surface of the hot-dip galvanized component, and obtain a corrosion-resistant hot-dip galvanized workpiece after the paint is cured.

2. The processing method according to claim 1, characterized in that The anti-corrosion coating comprises the following components in parts by weight: 30-50 parts of modified epoxy resin, 1-2 parts of antifreeze agent, 1-3 parts of defoaming agent, 10-20 parts of modified nano-silica, 1-3 parts of dispersant, 3-5 parts of curing agent, 15-20 parts of acetone.

3. The processing method according to claim 2, characterized in that The preparation method of the modified epoxy resin is as follows: Hexamethylene diisocyanate and terminal hydroxyl perfluoropolyether are mixed evenly and heated to react to obtain compound 1. Under a nitrogen atmosphere, compound 1 and epoxy resin are mixed evenly and heated to react for a period of time, and then stannous octoate is added to continue the reaction to obtain a modified epoxy resin.

4. The processing method according to claim 3, characterized in that: The mass ratio of the hexamethylene diisocyanate, the terminal hydroxyl perfluoropolyether and the epoxy resin is 2-4:1:10-15.

5. The processing method according to claim 2, characterized in that: The antifreeze agent is ethylene glycol or propylene glycol.

6. The processing method according to claim 2, characterized in that The defoaming agent is at least one of a phosphate hydrophobic defoaming agent, polysiloxane, and an organic alcohol compound.

7. The processing method according to claim 2, characterized in that: The dispersant is at least one of sodium tripolyphosphate, sodium hexametaphosphate, triethylhexyl phosphate, sodium lauryl sulfate, and methyl amyl alcohol.

8. The processing method according to claim 2, characterized in that: The preparation method of the modified nano-silica is as follows: dispersing nano-silica in a solvent, adding an aminosilane coupling agent, and heating to react to obtain amino-modified nano-silica; adding the amino-modified nano-silica to N,N-dimethylformamide, adding an aqueous solution of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4-imidazole acrylic acid, adjusting the pH value to be weakly acidic, heating to react, and collecting solids; dissolving dodecenylsuccinic acid in toluene, adding the solids and ammonium persulfate, and heating to react to obtain the modified nano-silica.

9. The processing method according to claim 8, characterized in that: The mass ratio of the amino-modified nano-silica, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution, 4-imidazole acrylic acid, and dodecenylsuccinic acid is 10-20:100:5-8:6-10.

10. The processing method according to claim 1 or 2, characterized in that: The preparation method of the anti-corrosion coating is as follows: weighing various raw materials according to a formula, mixing modified epoxy resin, antifreeze agent, defoaming agent, modified nano-silica, dispersant, curing agent and acetone, and stirring evenly to obtain the anti-corrosion coating.

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