High-corrosion-resistance composite hydrophobic coating for reinforcing steel bar for concrete and preparation method of high-corrosion-resistance composite hydrophobic coating

Abstract

The invention discloses a high-corrosion-resistance composite hydrophobic coating for a reinforcing steel bar for concrete and a preparation method thereof.The preparation method comprises the steps that the surface of a reinforcing steel bar sample is ground and polished, and then the reinforcing steel bar sample is cleaned and dried to obtain a pretreated reinforcing steel bar sample; immersing the pretreated reinforcing steel bar sample into an ethanol activation solution for activation treatment, and then rinsing with deionized water to obtain an activated reinforcing steel bar sample; a chemical plating solution is prepared, the activated steel bar sample is put into the chemical plating solution for chemical immersion plating, the sample is taken out and cleaned, and a Ni-P plating steel bar sample is obtained; an electrolyte is prepared, the Ni-P coating steel bar sample is immersed in the electrolyte for electrodeposition, the sample is taken out and cleaned, and a Ni-P / Ni composite coating steel bar sample is obtained; and preparing a hydrophobic solution, putting the Ni-P / Ni coating steel bar sample into the hydrophobic solution for dipping, taking out the sample, cleaning the sample, and blow-drying the sample by using a blower to obtain the Ni-P / Ni-SH hydrophobic composite coating steel bar sample. The coating prepared through the method is high in binding force with a steel bar base body and has high corrosion resistance and hydrophobicity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating, in particular to a high corrosion-resistant composite hydrophobic coating for steel bars used in concrete and a preparation method thereof. BACKGROUND

[0002] Reinforced concrete is a building material widely used in various engineering fields, but it is susceptible to steel durability problems. Due to carbonation and chloride ion penetration, the steel embedded in the concrete corrodes, and the corrosion of the steel in the concrete is one of the main reasons for the deterioration mechanism of the durability of reinforced concrete structures, especially in extreme chloride conditions in marine and coastal areas, chloride ions can reach the surface of the steel through the interconnected pores of the concrete and cause the generation and expansion of cracks, when the concentration of chloride ions exceeds the critical threshold on the steel surface, they locally destroy the passivation layer formed by iron oxides, hydroxides and hydroxyl oxides, resulting in the formation of a large amount of corrosion products, which will generate internal stress and cause the fracture of the reinforced concrete.

[0003] At present, the steel is mainly coated for corrosion protection, and the isolation of the coating prevents the steel from directly contacting with the corrosive medium, thereby playing a protective role. However, the existing steel surface coating has the problems of low corrosion resistance and low adhesion to the steel, which affects the durability and service life of the reinforced concrete. SUMMARY

[0004] To solve the above technical problems, the present application provides a high corrosion-resistant composite hydrophobic coating for steel bars used in concrete and a preparation method thereof.

[0005] The present application specifically adopts the following technical solutions:

[0006] The present application provides a preparation method of a high corrosion-resistant composite hydrophobic coating for steel bars used in concrete, comprising the following steps:

[0007] (1) polishing and polishing the surface of the steel bar sample, then cleaning and drying to obtain a pretreated steel bar sample;

[0008] (2) immersing the pretreated steel bar sample in an ethanol activation solution for activation treatment, then rinsing with deionized water to obtain an activated steel bar sample;

[0009] (3) configuring a chemical plating solution, immersing the activated steel bar sample in the chemical plating solution for chemical immersion plating, taking out the sample and cleaning to obtain a Ni-P plated steel bar sample;

[0010] (4) configuring an electrolyte, immersing the Ni-P plated steel bar sample in the electrolyte for electrodeposition, taking out the sample and cleaning to obtain a Ni-P / Ni composite plated steel bar sample;

[0011] (5) configuring a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution, taking out the sample and cleaning, and then drying with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0012] Further, the ethanol activation solution in the step (2) is a mixed solution obtained by dissolving an organic corrosion inhibitor and a surfactant in ethanol, the mass concentration of the organic corrosion inhibitor is 1-3%, the mass concentration of the surfactant is 0.2-0.8%, the activation treatment temperature is 20-25°C, and the activation treatment time is 10-25s.

[0013] Further, the components of the chemical plating solution in the step (3) are 15-40 μg / L of NiSO4, 10-30 μg / L of NaH2PO2H2O, 5-25 μg / L of CH3COONa, 6-20 μg / L of lactic acid preparation, 3-10 μg / L of complexing agent and 0.5-3 μg / L of whitening agent.

[0014] Further, the pH of the chemical plating solution in the step (3) is 3-5.6.

[0015] Further, the temperature of the chemical immersion plating in the step (3) is 50-120°C, and the time of the chemical immersion plating is 40-90 min.

[0016] Further, the components of the electrolyte in the step (4) are 10-30 g / L of NiCl2·6H2O, 1-6 g / L of NH4Cl and 10-20 g / L of H3BO3.

[0017] Further, the electrodeposition process in the step (4) is: immersing the Ni-P plated steel bar sample into the electrolyte, first electroplating at 35-60°C with a current of 1-6 A / dm 2 for 15-40 min to obtain a dense Ni deposition layer, and then continuing to electroplate for 1-3 min to roughen the surface of the Ni deposition layer.

[0018] Further, the hydrophobic solution in the step (5) is an alcohol solution of stearic acid, and the immersion time is 5-8 min.

[0019] Further, the concentration of the alcohol solution of stearic acid in the step (5) is 1-2.5 g / L.

[0020] The present application has the following beneficial effects:

[0021] (1) The application provides a preparation method of a high corrosion resistance composite hydrophobic coating for a steel bar for concrete, which comprises the following steps: firstly, a Ni-P plating layer is formed on the surface of the steel bar by chemical immersion plating, the plating layer can form a good metallurgical bond with the steel bar substrate, and can improve the bonding force between the coating and the substrate; then, a Ni layer is plated on the Ni-P plating layer and the Ni grows in situ on the Ni-P plating layer, so that the outer Ni layer can effectively fill the pores on the surface of the original Ni-P plating layer, effectively hinders the penetration of harmful ions to the surface of the substrate, and further reduces the corrosion current density after the Ni layer is plated again, thereby improving the corrosion resistance of the coating.

[0022] (2) In the application, the plating time of the Ni layer is controlled to form a dense Ni layer on the surface of the steel bar, and the Ni layer is continuously plated on the formed dense Ni layer to roughen the surface of the Ni layer, that is, a micro-rough structure surface is constructed, and then a stearic acid hydrophobic film is formed on the micro-rough structure surface, so that the hydrophobic performance of the coating is improved by using the micro-rough structure surface, and the corrosion resistance is further improved. DETAILED DESCRIPTION

[0023] The specific embodiments of the application are further described below in combination with specific examples.

[0024] Example 1

[0025] The application provides a preparation method of a high corrosion resistance composite hydrophobic coating for a steel bar for concrete, which comprises the following steps:

[0026] (1) Silicon carbide sandpaper (200-2000 mesh) is used to polish and polish the surface of the steel bar sample of Q355B material step by step until a smooth surface is obtained, then the sample is washed with deionized water, and degreased in an alcohol solution for 3 minutes to obtain a pretreated steel bar sample;

[0027] (2) The pretreated steel bar sample is immersed in an ethanol activation solution at 20℃ for activation treatment for 25s, and then rinsed with deionized water to obtain an activated steel bar sample; the ethanol activation solution in this step contains 2wt% organic corrosion inhibitor and 0.5wt% surfactant, the organic corrosion inhibitor is a benzotriazole substance, and the surfactant is sodium dodecyl sulfate, wherein the organic corrosion inhibitor forms a protective film on the surface of the steel bar to improve its corrosion resistance, and the surfactant can enhance the wettability of the solution on the surface of the steel bar to ensure uniform distribution of the activator;

[0028] (3) configuring a chemical plating solution consisting of 15 μg / L NiSO4, 10 μg / L NaH2PO2H2O, 5 μg / L CH3COONa, 6 μg / L lactic acid preparation, 3 μg / L complexing agent and 0.5 μg / L brightener, with pH = 3, and placing the activated steel bar sample into the chemical plating solution for chemical immersion plating at 50°C for 90 min, taking out the sample and washing with deionized water to obtain a Ni-P plated steel bar sample;

[0029] (4) configuring an electrolyte consisting of 10 g / L NiCl2·6H2O, 1 g / L NH4Cl and 15 g / L H3BO3, immersing the Ni-P plated steel bar sample into the electrolyte, first electroplating at 40°C for 15 min with a current of 6 A / dm2to obtain a dense Ni deposition layer, then continuing electroplating for 1 min to roughen the surface of the Ni deposition layer, taking out the sample and washing with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0030] (5) configuring an alcohol solution with a concentration of 1 g / L stearic acid as a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution for 8 min, taking out the sample and washing with deionized water, then blowing dry with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0031] Example 2

[0032] The embodiment provides a preparation method of a high corrosion-resistant composite hydrophobic coating for a steel bar for concrete, comprising the following steps:

[0033] (1) using silicon carbide sandpaper (200-2000 mesh) to gradually polish and polish the surface of a steel bar sample of Q355B material until a smooth surface is obtained, then washing the sample with deionized water and ultrasonically degreasing in an alcohol solution for 5 minutes to obtain a pretreated steel bar sample;

[0034] (2) immersing the pretreated steel bar sample into an ethanol activation solution at 23°C for activation treatment for 15 s, then rinsing with deionized water to obtain an activated steel bar sample; the ethanol activation solution in this step contains 1.5 wt% of an organic corrosion inhibitor and 0.2 wt% of a surfactant, and the organic corrosion inhibitor is a benzotriazole substance and the surfactant is sodium dodecyl sulfate;

[0035] ​(3) configuring a chemical plating solution consisting of 20 μg / L NiSO4, 15 μg / L NaH2PO2H2O, 10 μg / L CH3COONa, 12 μg / L lactic acid preparation, 5 μg / L complexing agent and 1.5 μg / L brightener, with pH = 3.5, and placing the activated steel bar sample into the chemical plating solution for chemical immersion plating at 70°C for 80 min, taking out the sample and washing with deionized water to obtain a Ni-P plated steel bar sample;

[0036] (4) configuring an electrolyte consisting of 15 g / L NiCl2·6H2O, 3 g / L NH4Cl and 10 g / L H3BO3, immersing the Ni-P plated steel bar sample into the electrolyte, first electroplating at 35°C for 30 min with a current of 3 A / dm2to obtain a dense Ni deposition layer, and then continuing electroplating for 1 min to roughen the surface of the Ni deposition layer, taking out the sample and washing with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0037] (5) configuring an alcohol solution with a concentration of 1.5 g / L stearic acid as a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution for 7 min, taking out the sample and washing with deionized water, and then blowing dry with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0038] Example 3

[0039] The present embodiment provides a method for preparing a high corrosion-resistant composite hydrophobic coating for a steel bar used in concrete, comprising the steps of:

[0040] (1) using silicon carbide sandpaper (200-2000 mesh) to gradually polish and polish the surface of a steel bar sample of Q355B material until a smooth surface is obtained, then washing the sample with deionized water and ultrasonically degreasing in an alcohol solution for 5 minutes to obtain a pretreated steel bar sample;

[0041] (2) immersing the pretreated steel bar sample into an ethanol activation solution at 25°C for activation treatment for 10 s, and then rinsing with deionized water to obtain an activated steel bar sample; the ethanol activation solution in this step contains 2.5 wt% organic corrosion inhibitor and 0.6 wt% surfactant, and the organic corrosion inhibitor is a benzotriazole substance and the surfactant is sodium dodecyl sulfate;

[0042] ​(3) configuring a chemical plating solution consisting of 25 μg / L NiSO4, 20 μg / L NaH2PO2H2O, 15 μg / L CH3COONa, 16 μg / L lactic acid preparation, 8 μg / L complexing agent and 2.5 μg / L brightener, with pH = 4, and placing the activated steel bar sample into the chemical plating solution for chemical immersion plating at 80°C for 70 min, taking out the sample and washing with deionized water to obtain a Ni-P plated steel bar sample;

[0043] (4) configuring an electrolyte consisting of 25 g / L NiCl2·6H2O, 5 g / L NH4Cl and 15 g / L H3BO3, immersing the Ni-P plated steel bar sample into the electrolyte, first electroplating at 55°C for 25 min with a current of 2 A / dm2to obtain a dense Ni deposition layer, then continuing electroplating for 1 min to roughen the surface of the Ni deposition layer, taking out the sample and washing with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0044] (5) configuring an alcohol solution with a concentration of 2 g / L stearic acid as a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution for 6 min, taking out the sample and washing with deionized water, then blowing dry with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0045] Example 4

[0046] The embodiment provides a preparation method of a high corrosion-resistant composite hydrophobic coating for a steel bar for concrete, comprising the following steps:

[0047] (1) using silicon carbide sandpaper (200-2000 mesh) to gradually polish and polish the surface of a steel bar sample of Q355B material until a smooth surface is obtained, then washing the sample with deionized water and ultrasonically degreasing in an alcohol solution for 5 minutes to obtain a pretreated steel bar sample;

[0048] (2) immersing the pretreated steel bar sample into an ethanol activation solution at 25°C for activation treatment for 10 s, then rinsing with deionized water to obtain an activated steel bar sample; the ethanol activation solution in this step contains 3.0 wt% of an organic corrosion inhibitor and 0.8 wt% of a surfactant, and the organic corrosion inhibitor is a benzotriazole substance and the surfactant is sodium dodecyl sulfate;

[0049] ​(3) configuring a chemical plating solution consisting of 30 μg / L NiSO4, 25 μg / L NaH2PO2H2O, 20 μg / L CH3COONa, 18 μg / L lactic acid preparation, 10 μg / L complexing agent and 2 μg / L whitening agent, with pH = 5, and placing the activated steel bar sample into the chemical plating solution for chemical immersion plating at 90°C for 60 min, taking out the sample and washing with deionized water to obtain a Ni-P plated steel bar sample;

[0050] (4) configuring an electrolyte consisting of 30 g / L NiCl2·6H2O, 6 g / L NH4Cl and 20 g / L H3BO3, immersing the Ni-P plated steel bar sample into the electrolyte, first electroplating at 50°C for 20 min with a current of 4 A / dm2to obtain a dense Ni deposition layer, then continuing electroplating for 2 min to roughen the surface of the Ni deposition layer, taking out the sample and washing with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0051] (5) configuring an alcohol solution with a concentration of 2.5 g / L stearic acid as a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution for 5 min, taking out the sample and washing with deionized water, then blowing dry with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0052] Example 5

[0053] The embodiment provides a preparation method of a high corrosion-resistant composite hydrophobic coating for a steel bar for concrete, comprising the following steps:

[0054] (1) using silicon carbide sandpaper (200-2000 mesh) to gradually polish and polish the surface of a steel bar sample of Q355B material until a smooth surface is obtained, then washing the sample with deionized water and ultrasonically degreasing in an alcohol solution for 5 minutes to obtain a pretreated steel bar sample;

[0055] (2) immersing the pretreated steel bar sample into an ethanol activation solution at 25°C for activation treatment for 10 s, then rinsing with deionized water to obtain an activated steel bar sample; the ethanol activation solution in this step contains 2 wt% of an organic corrosion inhibitor and 0.5 wt% of a surfactant, and the organic corrosion inhibitor is a benzotriazole substance and the surfactant is sodium dodecyl sulfate;

[0056] ​(3) configuring a chemical plating solution consisting of 35 μg / L NiSO4, 28 μg / L NaH2PO2H2O, 25 μg / L CH3COONa, 20 μg / L lactic acid preparation, 6 μg / L complexing agent and 3 μg / L brightener, with pH = 5.5, and placing the activated steel bar sample into the chemical plating solution to perform chemical immersion plating at 100°C for 50 min, taking out the sample and washing with deionized water to obtain a Ni-P plated steel bar sample;

[0057] (4) configuring an electrolyte consisting of 20 g / L NiCl2·6H2O, 2 g / L NH4Cl and 18 g / L H3BO3, immersing the Ni-P plated steel bar sample into the electrolyte, first performing electroplating at 45°C for 35 min with a current of 5 A / dm2to obtain a dense Ni deposition layer, then continuing electroplating for 2 min to roughen the surface of the Ni deposition layer, taking out the sample and washing with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0058] (5) configuring an alcohol solution with a concentration of 1.5 g / L stearic acid as a hydrophobic solution, immersing the Ni-P / Ni plated steel bar sample into the hydrophobic solution for 8 min, taking out the sample and washing with deionized water, then blowing dry with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0059] Example 6

[0060] The embodiment provides a preparation method of a high corrosion-resistant composite hydrophobic coating for a steel bar for concrete, comprising the following steps:

[0061] (1) using silicon carbide sandpaper (200-2000 mesh) to perform step-by-step polishing and polishing on the surface of a steel bar sample of Q355B material until a smooth surface is obtained, then washing the sample with deionized water and performing ultrasonic degreasing in an alcohol solution for 5 min to obtain a pretreated steel bar sample;

[0062] (2) immersing the pretreated steel bar sample into an ethanol activation solution at 25°C to perform activation treatment for 10 s, then rinsing with deionized water to obtain an activated steel bar sample; the ethanol activation solution contains 2 wt% of an organic corrosion inhibitor and 0.5 wt% of a surfactant in this step, the organic corrosion inhibitor is a benzotriazole substance, and the surfactant is sodium dodecyl sulfate;

[0063] ​(3) A chemical plating solution consisting of 40 μg / L NiSO4, 30 μg / L NaH2PO2H2O, 25 μg / L CH3COONa, 10 μg / L lactic acid preparation, 5 μg / L complexing agent and 1 μg / L whitening agent is configured, and the pH value is 5.6. The activated steel bar sample is placed in the chemical plating solution and subjected to chemical immersion plating at 120°C for 40 min. The sample is taken out and washed with deionized water to obtain a Ni-P plated steel bar sample;

[0064] (4) An electrolyte solution consisting of 25 g / L NiCl2·6H2O, 4 g / L NH4Cl and 12 g / L H3BO3 is configured. The Ni-P plated steel bar sample is immersed in the electrolyte solution, and first subjected to electroplating at 60°C for 40 min at a current of 1 A / dm2to obtain a compact Ni deposition layer. Then, the electroplating is continued for 3 min to roughen the surface of the Ni deposition layer. The sample is taken out and washed with deionized water to obtain a Ni-P / Ni composite plated steel bar sample; 2

[0065] (5) An alcohol solution with a concentration of 1.5 g / L of stearic acid is configured as a hydrophobic solution. The Ni-P / Ni plated steel bar sample is immersed in the hydrophobic solution for 8 min. The sample is taken out and washed with deionized water, and then dried with a hair dryer to obtain a Ni-P / Ni-SH hydrophobic composite plated steel bar sample.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that, in this comparative example, after the compact Ni deposition layer is formed in step (4), the electroplating is not continued to roughen the surface of the Ni deposition layer. The other steps are the same as those in Example 1.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that, in this comparative example, a one-step chemical immersion plating is used to form a Ni-P / Ni composite plated layer on the surface of the steel bar. The chemical plating solution consists of 15 μg / L NiSO4, 10 μg / L NaH2PO2H2O, 5 μg / L CH3COONa, 6 μg / L lactic acid preparation, 3 μg / L complexing agent, 0.5 μg / L whitening agent, 10 g / L NiCl2·6H2O, 1 g / L NH4Cl and 15 g / L H3BO3. The steel bar sample is placed in the chemical plating solution and subjected to chemical immersion plating at 50°C for 90 min. The other steps are the same as those in Example 1.

[0070] The Ni-P / Ni-SH hydrophobic composite plated steel bar samples prepared in Examples 1-6 and Comparative Examples 1 and 2 above are subjected to microscopic morphology testing, mechanical property testing, corrosion resistance testing and hydrophobicity testing. The test results are shown in Table 1 below.

[0071] ​The mechanical property testing method is: the testing of the mechanical property of the coating mainly refers to the testing of the microhardness of the coating, and the hardness can reflect the bonding force of the coating and the substrate, and generally the higher the hardness, the stronger the bonding force. The test method is: under the action of a specified test force, a diamond right tetrahedron indenter with a top angle of 136° between two opposite faces is pressed into the surface of the sample, and the test force is kept for a certain time, and then the test force is unloaded, and the length of the diagonal line of the indentation on the surface of the sample is measured. The hardness value is equal to the test force divided by the surface area of the indentation. In this embodiment, a microhardness tester with a model of MH-3 is used to test the hardness of the coating, the test force is 200-500 g, the pressure holding time is 5-8 s, five points of each sample are tested, and the average value is taken as the microhardness of the coating.

[0072] The corrosion resistance testing method is: electrochemical testing analysis is used, and the potentiodynamic polarization curve is tested, and then the corrosion current density and the corrosion potential are analyzed. The smaller the corrosion current density, the slower the corrosion speed, and the better the corrosion resistance. In the testing process, a three-electrode system is used, in which a platinum electrode is used as an auxiliary electrode, a sample electrode is used as a working electrode, and a saturated calomel electrode is used as a reference electrode; the test solution is a 3.5wt.% NaCl solution simulating the marine atmospheric environment; the test temperature is 25°C, the scanning interval is ±300mV, and the scanning speed is 1mV / s.

[0073] Table 1

[0074]

[0075] The data in Table 1 is analyzed. Compared with Comparative Example 2, the microhardness of the Ni-P / Ni-SH hydrophobic composite coating steel bar sample prepared in Examples 1-6 is obviously high, which indicates that the bonding force of the coating prepared by the method of Examples 1-6 to the steel bar substrate is high. Moreover, the corrosion current density of the Ni-P / Ni-SH hydrophobic composite coating steel bar sample prepared in Examples 1-6 is obviously small, which indicates that the coating has good corrosion resistance and can improve the corrosion resistance of the steel bar substrate. In addition, compared with Comparative Example 1, the water contact angle of the Ni-P / Ni-SH hydrophobic composite coating steel bar sample prepared in Examples 1-6 is large, and the hydrophobicity is better. The main reason is that the coating surface prepared in Examples 1-6 has a micro-rough structure, which can further improve the hydrophobicity of the hydrophobic coating.

[0076] It should be noted that the parts not described in this embodiment are obtained by using the prior art.

[0077] Of course, the above description is not a limitation on the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A method for preparing a highly corrosion-resistant composite hydrophobic coating for concrete reinforcing bars, characterized in that, Including the following steps: (1) Grind and polish the surface of the steel bar sample, then clean and dry it to obtain a pretreated steel bar sample; (2) The pretreated steel bar sample was immersed in an ethanol activation solution for activation treatment, and then rinsed with deionized water to obtain the activated steel bar sample. (3) Prepare a chemical plating solution, immerse the activated steel bar sample in the chemical plating solution for chemical plating, remove the sample and clean it to obtain a Ni-P coated steel bar sample. (4) Prepare an electrolyte solution, immerse the Ni-P coated steel bar sample in the electrolyte solution for electrodeposition, take out the sample and clean it to obtain a Ni-P / Ni composite coated steel bar sample. (5) Prepare a hydrophobic solution, immerse the Ni-P / Ni coated steel bar sample in the hydrophobic solution, take out the sample and clean it, and then dry it with a hair dryer to obtain the Ni-P / Ni-SH hydrophobic composite coated steel bar sample.

2. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, In step (2), the ethanol activation solution is a mixed solution obtained by dissolving an organic corrosion inhibitor and a surfactant in ethanol, and the mass concentration of the organic corrosion inhibitor is 1% to 3% and the mass concentration of the surfactant is 0.2% to 0.8%; the activation treatment temperature is 20 to 25°C and the activation treatment time is 10 to 25 seconds.

3. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, The chemical plating solution in step (3) consists of 15–40 μg / L NiSO4, 10–30 μg / L NaH2PO2H2O, 5–25 μg / L CH3COONa, 6–20 μg / L lactic acid preparation, 3–10 μg / L complexing agent, and 0.5–3 μg / L whitening agent.

4. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, The pH of the chemical plating solution in step (3) is 3 to 5.

6.

5. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, In step (3), the temperature of chemical immersion plating is 50-120℃, and the time of chemical immersion plating is 40-90 min.

6. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, The electrolyte in step (4) consists of 10–30 g / L NiCl2·6H2O, 1–6 g / L NH4Cl, and 10–20 g / L H3BO3.

7. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, The electrodeposition process in step (4) is as follows: the Ni-P coated steel bar sample is immersed in the electrolyte, and first at 35-60℃ with an electrodeposition rate of 1-6 A / dm. 2 A dense Ni deposition layer is obtained by electroplating with a current for 15–40 min, and then electroplating is continued for 1–3 min to roughen the surface of the Ni deposition layer.

8. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 1, characterized in that, In step (5), the hydrophobic solution is an alcoholic solution of stearic acid, and the immersion time is 5 to 8 minutes.

9. The method for preparing a high corrosion-resistant composite hydrophobic coating for concrete reinforcing bars according to claim 8, characterized in that, In step (5), the concentration of the alcoholic solution of stearic acid is 1 to 2.5 g / L.

10. A highly corrosion-resistant composite hydrophobic coating for concrete reinforcing bars, prepared by the preparation method according to any one of claims 1-9.

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