Method for accelerating stabilization of rust layer on surface of weathering resistant steel

Abstract

The invention discloses a method for accelerating stabilization of a rust layer on the surface of weathering resistant steel, and relates to a method capable of increasing the stabilization speed of the rust layer on the surface of the weathering resistant steel. The invention aims to solve the problem of slow formation speed of a protective rust layer on the surface of the weathering steel at present. The method for accelerating stabilization of the rust layer on the surface of the weathering resistant steel comprises the following steps: (1) preparing a pulse plating solution; (2) pulse electroplating; (3) double-pulse electroplating; and (4) coating the gel. According to the method for accelerating stabilization of the rust layer on the surface of the weathering resistant steel, the stabilization process of the rust layer on the surface of the weathering resistant steel can be shortened, and rapid formation of the stable rust layer with excellent corrosion resistance is achieved.

Description

Technical Field

[0001] The invention belongs to the field of anti-corrosion treatment of weathering steel, and in particular relates to a method for accelerating the stabilization of rust layer on the surface of weathering steel. Background Art

[0002] The information disclosed in this background technology section is only intended to increase some understanding of the overall background of the invention, and should not be necessarily regarded as an admission or any form of suggestion that the information constitutes the prior art already known to ordinary technicians in this field.

[0003] Weathering steel is a low alloy steel. During the steel smelting process, the corrosion resistance of the steel is greatly improved by adding elements such as Cu, Cr, Ni, and P, which is even several times that of ordinary carbon steel, so as to achieve the purpose of corrosion resistance. The reason why weathering steel has excellent corrosion resistance is that it can form a dense and stable protective rust layer after long-term use in a certain environment, thereby hindering the further erosion of the substrate by the corrosive medium. In other words, the anti-corrosion layer of weathering steel is the rust layer formed by itself. In the process of forming the protective rust layer on the surface of weathering steel, the formation of α-FeOOH is very important, and elements such as Cu, Cr, Ni, and P will promote the formation of a protective rust layer with α-FeOOH as the core. After the protective rust layer is formed, the corrosion rate of the corrosive medium on the substrate will be greatly reduced, thereby ensuring that the weathering steel has corrosion resistance that ordinary carbon steel cannot match.

[0004] Due to the excellent corrosion resistance of weathering steel, it can be used directly without any anti-corrosion treatment in ordinary atmospheric environment, thus saving a lot of painting and subsequent maintenance costs, and the economic benefits are significant. In addition, weathering steel also has good mechanical properties and weldability, so it is widely used in the construction process of infrastructure such as steel structure bridges. However, the formation of rust layer on the surface of weathering steel often takes several years. If the weathering steel encounters special meteorological and hydrological conditions before the stable rust layer is formed, the formed surface rust layer is a loose structure without protective performance, which is not conducive to the long-term use of weathering steel. In order to extend the life cycle of weathering steel and enhance the corrosion resistance of weathering steel, it is often necessary to accelerate the stabilization of the rust layer of weathering steel in the early stage of use, so as to quickly generate a surface rust layer with excellent corrosion resistance. Therefore, the development of efficient methods to accelerate the stabilization of the rust layer on the surface of weathering steel is of great significance for extending the life cycle of weathering steel. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to solve the problems of long rust layer formation period and unsatisfactory protectiveness on the surface of weathering steel, and to provide a method for accelerating the formation of a protective stabilized rust layer on the surface of weathering steel.

[0006] The technical solution adopted by the present invention is as follows:

[0007] In a first aspect of the present invention, a method for accelerating the stabilization of the rust layer on the surface of weathering steel is provided, the method comprising the following steps:

[0008] (1) Preparation of pulse plating solution: Weigh citric acid and dissolve it in water, then dissolve hydroquinone, thiourea and 5,5-dimethylhydantoin, then add copper powder and cobalt hydroxide, stir at 60-80 °C and filter out insoluble matter, then adjust the pH by adding sodium citrate, finally add sodium sulfide solution and make up to volume to obtain pulse plating solution;

[0009] (2) Pulse plating: The weathering steel with the oil removed from the surface is connected to the negative electrode of the pulse power supply, and the copper plate is connected to the positive electrode of the pulse power supply. The two electrodes are separated by a sponge soaked in the pulse plating solution. The pulse power supply is set to output a steady current. After electroplating, the pulse plating is completed. The parameters of a single pulse cycle in the pulse plating process are set as follows: the output peak current is 18~22.5A, the duty cycle is 10~20%, and the frequency is 100~200 Hz;

[0010] (3) Double pulse electroplating: the weathering steel treated in step (2) is connected to the negative electrode of the double pulse power supply, and the copper plate is connected to the positive electrode of the double pulse power supply. The two electrodes are separated by a sponge soaked in a pulse plating solution, and the double pulse power supply is set to output a steady current. After electroplating, the double pulse electroplating is completed; wherein the parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 18-22.5 A, the duty cycle is 10-20%, the frequency is 50-100 Hz, and the number of pulses is 1; the output negative pulse peak current is 27-33.75 A, the duty cycle is 10-20%, the frequency is 100-200 Hz, and the number of pulses is 1;

[0011] (4) applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 1-2 wt% agar, 2-3 wt% sodium polyphosphate, 0.05-0.1 wt% tannic acid, 3-5 wt% sodium chloride, and the rest is water.

[0012] In one or more embodiments of the present invention, in step (1), the feed ratio of citric acid, water, hydroquinone, thiourea, 5,5-dimethylhydantoin, copper powder, cobalt hydroxide, and sodium sulfide solution is (40-50) g: (850-950) mL: (6-8) g: (80-100) g: (15-20) g: (15-20) g: (3-5) g: (40-60) mL, and the concentration of the sodium sulfide solution is 2-3 g / L.

[0013] In step (1), the particle size of the copper powder is 500-300 mesh.

[0014] In step (1), stirring is performed for 4.5 to 5.5 hours. Preferably, stirring is performed for 5 hours.

[0015] In step (1), the pH is adjusted to 4.5-5.5. Preferably, the pH is adjusted to 5.

[0016] In one or more embodiments of the present invention, in step (2), the electroplating time is 0.5 to 1.5 minutes. Preferably, the electroplating time is 1 minute.

[0017] In one or more embodiments of the present invention, in step (3), the electroplating time is 3 to 5 minutes.

[0018] In one or more embodiments of the present invention, the pulse plating solution used in step (2) and step (3) operates at a temperature not lower than 45°C.

[0019] In the process of preparing the pulse plating solution in step (1), by adding thiourea, a strong chelating agent for copper, into a solution containing citric acid, the copper powder can undergo a significant negative shift in potential under the action of thiourea after being added, thereby reacting with the acid to form a monovalent copper salt. When sodium citrate is added, the pH value of the solution can be adjusted and the stability of the monovalent copper salt can be further enhanced. Hydroquinone is an antioxidant that can make thiourea and monovalent copper salts stable in the solution for a long time; dimethylhydantoin is an auxiliary complexing agent for monovalent copper salts, which can complex cuprous ions with thiourea and citrate, thereby making copper powder easier to complex and dissolve, making the obtained cuprous ions more stable, and making the cuprous ions better electrochemically reduced during the pulse electroplating process; cobalt hydroxide can react with citric acid during the preparation of the pulse plating solution to dissolve cobalt ions in the pulse plating solution; the sodium sulfide content in the pulse plating solution is very low, and the cuprous ions and cobalt ions in the plating solution can coexist with it in the presence of a complexing agent, but in the double pulse electroplating process, when the anode pulse current passes, the large amount of cuprous ions and cobalt ions generated instantly can be partially converted into insoluble cuprous sulfide and cobalt sulfide with sodium sulfide, thereby forming a composite deposition layer. In the pulse electroplating process of step (2), weathering steel is used as the cathode, and the cathode current density is 2~2.5 A / dm 2 At this cathode current density, the surface of the weathering steel can electrochemically reduce copper and trace amounts of cobalt. A duty cycle of 10-20% can effectively alleviate concentration polarization. In the double pulse electroplating process of step (3), the weathering steel plated with copper and cobalt periodically passes through the cathode pulse current and the anode pulse current. When the cathode pulse current is passed, the cathode current density is 2-2.5 A / dm 2 , weathering steel acts as the cathode to deposit copper and trace amounts of cobalt; when an anodic pulse current is passed through, the anodic current density is 3~3.75 A / dm2 , copper oxidation process, cobalt oxidation process and other side reactions occur; the duty cycle of 10-20% can effectively alleviate concentration polarization. Since the pulse plating solution contains a large amount of thiourea, the copper oxidation process will be converted into monovalent copper when the anode pulse current passes through. Since the pulse plating solution also contains a small amount of sulfur ions, copper will be partially converted into insoluble cuprous sulfide, and cobalt will be partially converted into cobalt sulfide. After double pulse electroplating, a composite deposition layer of copper, cobalt, cuprous sulfide and cobalt sulfide can be obtained. After step (4) of applying the gel, since the composite deposition layer cannot completely cover the weathering steel, the gel can simultaneously contact the weathering steel substrate and the coating to form a corrosion galvanic cell. The coating with a more positive potential acts as the cathode of the corrosion galvanic cell, and the weathering steel substrate with a more negative potential acts as the anode of the corrosion galvanic cell, causing rust to form a rust layer. Since the deposition layer is mixed with cuprous sulfide and cobalt sulfide, it can act as a catalyst for oxygen reduction, accelerating the cathode process of corrosion, which is conducive to the faster formation of a stable rust layer. In addition, when the rust layer is aged in an open space outdoors, ultraviolet rays can induce the semiconductor cuprous sulfide and cobalt sulfide to produce photogenerated electrons and photogenerated holes. The photogenerated holes are oxidizing and thus accelerate the formation of the rust layer. In addition, cuprous sulfide can inhibit the growth of microorganisms. In the long run, it can also prevent the attachment of microorganisms during the rust layer formation process, thereby preventing the reduction of the α-FeOOH content in the rust layer and the degradation of protective properties. In the process of generating the rust layer, the chloride ions in the gel can accelerate the corrosion process. Tannic acid can form a sparingly soluble complex with iron to accelerate the corrosion process. At the same time, the sparingly soluble complex that can be generated can promote the stabilization of the rust layer, which is beneficial to the improvement of the corrosion resistance of the rust layer. Sodium polyphosphate can act as a water retaining agent in the process of generating the rust layer, thereby maintaining the long-term existence of the water film and forming a corrosion microbattery. Therefore, after being treated in step (4), a protective rust layer can be formed on the surface of the weathering steel in a short time, which has a significant effect on improving the long-term corrosion resistance of the weathering steel.

[0020] In a second aspect of the present invention, there is provided a rust layer on the surface of weathering steel prepared by the method described in the first aspect.

[0021] In a third aspect of the present invention, a weathering steel having a surface rust layer as described in the second aspect is provided.

[0022] Compared with the related art known to the inventor, one of the technical solutions of the present invention has the following beneficial effects:

[0023] The present invention provides a method for accelerating the stabilization of the rust layer on the surface of weathering steel, which can significantly shorten the formation time of the stabilized rust layer, thereby improving the corrosion resistance of the weathering steel, solving the problem of the long formation period of the protective rust layer of the weathering steel during use, and has good economic benefits for steel structure projects using weathering steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is the SEM image of the weathering steel without any treatment in test 1;

[0026] Figure 2 SEM images of weathering steel after pulse plating and double pulse plating for test 1;

[0027] Figure 3 This is the SEM image of the weathering steel after 15 days of gel coating in test 1;

[0028] Figure 4 These are the EIS curves of weathering steel with accelerated surface rust stabilization in experiments 1 to 5 and weathering steel without any treatment measured at open circuit potential in 3.5 wt% NaCl solution. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0031] In a typical embodiment of the present invention, a method for accelerating the stabilization of the rust layer on the surface of weathering steel is provided, which is carried out in the following steps:

[0032] (1) Preparation of pulse plating solution: Weigh 40-50 g of citric acid and dissolve it in 900 mL of deionized water, then dissolve 6-8 g of hydroquinone, 80-100 g of thiourea and 15-20 g of 5,5-dimethylhydantoin in sequence, then add 15-20 g of copper powder and 3-5 g of cobalt hydroxide, stir at 60-80 °C for 5 h, filter out the insoluble matter, then adjust the pH to 5.0 by adding sodium citrate, finally slowly add 50 mL of sodium sulfide solution and dilute to 1 L to prepare the pulse plating solution;

[0033] (2) Pulse plating: The weathering steel with the oil removed from the surface was connected to the negative electrode of the pulse power supply, and the copper plate with an area of ​​9 square decimeters was connected to the positive electrode of the pulse power supply. The two electrodes were separated by a sponge soaked in the pulse plating solution. The pulse power supply was set to output a steady current. The pulse plating was completed after 1 min. The parameters of a single pulse cycle in the pulse plating process were set as follows: the output peak current was 18~22.5 A, the duty cycle was 10~20%, and the frequency was 100~200 Hz.

[0034] (3) Double pulse electroplating: connect the weathering steel treated in step (2) to the negative electrode of the double pulse power supply, connect the copper plate with an area of ​​9 square decimeters to the positive electrode of the double pulse power supply, separate the two electrodes with a sponge soaked in pulse plating solution, set the double pulse power supply to output a steady current, and complete the double pulse electroplating after electroplating for 3 to 5 minutes; wherein the parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 18 to 22.5 A, the duty cycle is 10 to 20%, the frequency is 50 to 100 Hz, the number of pulses is 1, and the output negative pulse peak current is 27 to 33.75 A, the duty cycle is 10 to 20%, the frequency is 100 to 200 Hz, and the number of pulses is 1;

[0035] (4) applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 1-2 wt% agar, 2-3 wt% sodium polyphosphate, 0.05-0.1 wt% tannic acid, 3-5 wt% sodium chloride, and the rest is water.

[0036] In step (1), the particle size of the copper powder is 500-300 mesh.

[0037] In step (1), the concentration of the sodium sulfide solution is 2-3 g / L.

[0038] In step (2) and step (3), the working temperature of the pulse plating solution used is not less than 45°C.

[0039] In the process of preparing the pulse plating solution in step (1), copper powder can react with acid under the action of thiourea to generate monovalent copper salt. The citric acid / sodium citrate system can not only adjust the pH of the solution, but also serve as an auxiliary complexing agent to enhance the stability of the monovalent copper salt. In the pulse electroplating process of step (2), copper and trace amounts of cobalt can be electrochemically reduced on the surface of the weathering steel. The duty cycle of 10-20% can alleviate concentration polarization. In the double pulse electroplating process of step (3), when the cathode pulse current passes, copper and trace amounts of cobalt are deposited on the surface of the weathering steel. When the anode pulse current passes, copper is oxidized to monovalent copper, cobalt is oxidized, and other side reactions occur. The duty cycle of 10-20% can alleviate concentration polarization. Since the pulse plating solution also contains a small amount of sulfur ions, copper will be partially converted into insoluble cuprous sulfide and cobalt will be partially converted into cobalt sulfide when the anode pulse current passes. After double pulse electroplating, a composite deposition layer of copper, cobalt, cuprous sulfide and cobalt sulfide can be obtained. After the gel is applied in step (4), since the composite deposition layer cannot completely cover the weathering steel, the gel can contact the weathering steel substrate and the coating at the same time to form a corrosion galvanic cell. The coating with a more positive potential acts as the cathode of the corrosion galvanic cell, and the weathering steel substrate with a more negative potential acts as the anode of the corrosion galvanic cell, which causes rust to form a rust layer. Since cuprous sulfide and cobalt sulfide are mixed in the deposition layer, they can act as catalysts for oxygen reduction, accelerating the cathode process of corrosion, which is conducive to the faster formation of a stabilized rust layer. In addition, when the rust layer is aged in an open space outdoors, ultraviolet rays can induce semiconductor cuprous sulfide and cobalt sulfide to generate photogenerated electrons and photogenerated holes. The photogenerated holes are oxidizing and thus accelerate the formation of the rust layer. In addition, cuprous sulfide can inhibit the growth of microorganisms. In the long run, it can also prevent the attachment of microorganisms during the rust layer formation process, thereby reducing the α-FeOOH content in the rust layer and degrading the protective properties. In the process of generating the rust layer, the chloride ions in the gel can accelerate the corrosion process, and the tannic acid can form an insoluble complex with iron to accelerate the corrosion process. At the same time, the insoluble complex generated can promote the stabilization of the rust layer, which is beneficial to the improvement of the corrosion resistance of the rust layer. Therefore, after the treatment of step (4), a protective rust layer can be formed on the surface of the weathering steel in a short time, solving the problem of the long protective rust layer formation period of the weathering steel during use, thereby having a significant effect on improving the long-term corrosion resistance of the weathering steel.

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0041] Example 1

[0042] A method for accelerating the stabilization of the rust layer on the surface of weathering steel, the method comprising the following steps:

[0043] (1) Preparation of pulse plating solution: Weigh 40 g of citric acid and dissolve it in 900 mL of deionized water, then dissolve 6 g of hydroquinone, 80 g of thiourea and 20 g of 5,5-dimethylhydantoin in sequence, then add 15 g of copper powder and 3 g of cobalt hydroxide, stir at 80 °C for 5 h, filter out the insoluble matter, then adjust the pH to 5.0 by adding sodium citrate, finally slowly add 50 mL of sodium sulfide solution and dilute to 1 L to prepare the pulse plating solution;

[0044] (2) Pulse plating: The weathering steel with the oil removed from the surface was connected to the negative electrode of the pulse power supply, and the copper plate with an area of ​​9 square decimeters was connected to the positive electrode of the pulse power supply. The two electrodes were separated by a sponge soaked in the pulse plating solution. The pulse power supply was set to output a steady current. The pulse plating was completed after 1 min. The parameters of a single pulse cycle in the pulse plating process were set as follows: the output peak current was 18 A, the duty cycle was 10%, and the frequency was 200 Hz.

[0045] (3) Double pulse electroplating: the weathering steel treated in step (2) is connected to the negative electrode of the double pulse power supply, and the copper plate with an area of ​​9 square decimeters is connected to the positive electrode of the double pulse power supply. The two electrodes are separated by a sponge soaked in a pulse plating solution. The double pulse power supply is set to output a steady current. The double pulse electroplating is completed after electroplating for 5 minutes. The parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 18 A, the duty cycle is 10%, the frequency is 100 Hz, and the number of pulses is 1; the output negative pulse peak current is 27 A, the duty cycle is 10%, the frequency is 200 Hz, and the number of pulses is 1;

[0046] (4) applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 1 wt% agar, 3 wt% sodium polyphosphate, 0.1 wt% tannic acid, 3 wt% sodium chloride, and the remainder water.

[0047] The particle size of the copper powder in step (1) is 500 mesh; the concentration of the sodium sulfide solution in step (1) is 2 g / L; the working temperature of the pulse plating solution used in step (2) and step (3) is not less than 60°C.

[0048] Example 2

[0049] A method for accelerating the stabilization of the rust layer on the surface of weathering steel, the method comprising the following steps:

[0050] (1) Preparation of pulse plating solution: weigh 50 g of citric acid and dissolve it in 900 mL of deionized water, then dissolve 8 g of hydroquinone, 100 g of thiourea and 15 g of 5,5-dimethylhydantoin in sequence, then add 20 g of copper powder and 5 g of cobalt hydroxide, stir at 60 °C for 5 h, filter out the insoluble matter, then adjust the pH to 5.0 by adding sodium citrate, finally slowly add 50 mL of sodium sulfide solution and dilute to 1 L to prepare the pulse plating solution;

[0051] (2) Pulse plating: The weathering steel with the oil removed from the surface was connected to the negative electrode of the pulse power supply, and the copper plate with an area of ​​9 square decimeters was connected to the positive electrode of the pulse power supply. The two electrodes were separated by a sponge soaked in the pulse plating solution. The pulse power supply was set to output a steady current. The pulse plating was completed after 1 min. The parameters of a single pulse cycle in the pulse plating process were set as follows: the output peak current was 22.5 A, the duty cycle was 20%, and the frequency was 100 Hz.

[0052] (3) Double pulse electroplating: connect the weathering steel treated in step (2) to the negative electrode of the double pulse power supply, connect the copper plate with an area of ​​9 square decimeters to the positive electrode of the double pulse power supply, separate the two electrodes with a sponge soaked in pulse plating solution, set the double pulse power supply to output a steady current, and complete the double pulse electroplating after electroplating for 3 minutes; wherein the parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 22.5 A, the duty cycle is 20%, the frequency is 50 Hz, the number of pulses is 1, and the output negative pulse peak current is 33.75 A, the duty cycle is 20%, the frequency is 100 Hz, and the number of pulses is 1;

[0053] (4) applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 2 wt% agar, 2 wt% sodium polyphosphate, 0.05 wt% tannic acid, 5 wt% sodium chloride, and the remainder is water.

[0054] The particle size of the copper powder in step (1) is 300 mesh; the concentration of the sodium sulfide solution in step (1) is 3 g / L; the working temperature of the pulse plating solution used in steps (2) and (3) is not less than 45°C.

[0055] Example 3

[0056] A method for accelerating the stabilization of the rust layer on the surface of weathering steel, the method comprising the following steps:

[0057] (1) Preparation of pulse plating solution: Weigh 45 g of citric acid and dissolve it in 900 mL of deionized water, then dissolve 7 g of hydroquinone, 90 g of thiourea and 16 g of 5,5-dimethylhydantoin in sequence, then add 18 g of copper powder and 3.5 g of cobalt hydroxide, stir at 65 °C for 5 h, filter out the insoluble matter, then adjust the pH to 5.0 by adding sodium citrate, finally slowly add 50 mL of sodium sulfide solution and dilute to 1 L to prepare the pulse plating solution;

[0058] (2) Pulse plating: The weathering steel with the oil removed from the surface was connected to the negative electrode of the pulse power supply, and the copper plate with an area of ​​9 square decimeters was connected to the positive electrode of the pulse power supply. The two electrodes were separated by a sponge soaked in the pulse plating solution. The pulse power supply was set to output a steady current. The pulse plating was completed after 1 min. The parameters of a single pulse cycle in the pulse plating process were set as follows: the output peak current was 20.25 A, the duty cycle was 15%, and the frequency was 150 Hz.

[0059] (3) Double pulse electroplating: the weathering steel treated in step (2) is connected to the negative electrode of the double pulse power supply, and the copper plate with an area of ​​9 square decimeters is connected to the positive electrode of the double pulse power supply. The two electrodes are separated by a sponge soaked in a pulse plating solution. The double pulse power supply is set to output a steady current. The double pulse electroplating is completed after electroplating for 4 minutes. The parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 20.25 A, the duty cycle is 15%, the frequency is 60 Hz, and the number of pulses is 1; the output negative pulse peak current is 31.5 A, the duty cycle is 15%, the frequency is 150 Hz, and the number of pulses is 1;

[0060] (4) Applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 1.5 wt% agar, 2.5 wt% sodium polyphosphate, 0.06 wt% tannic acid, 3.5 wt% sodium chloride, and the remainder water.

[0061] The particle size of the copper powder in step (1) is 400 mesh; the concentration of the sodium sulfide solution in step (1) is 2.5 g / L; the working temperature of the pulse plating solution used in steps (2) and (3) is not less than 50°C.

[0062] Example 4

[0063] The difference from Example 3 is that:

[0064] In step (2), the parameters of a single pulse cycle during the pulse electroplating process are set as follows: output peak current is 22.5 A, duty cycle is 10%, and frequency is 100 Hz.

[0065] The other steps and methods are the same as those in Example 3.

[0066] Example 5

[0067] The difference from Example 3 is that:

[0068] In step (3), the parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 22.5 A, the duty cycle is 10%, the frequency is 100 Hz, and the number of pulses is 1; the output negative pulse peak current is 33.75 A, the duty cycle is 10%, the frequency is 200 Hz, and the number of pulses is 1.

[0069] The other steps and methods are the same as those in Example 3.

[0070] The following test verifies that the present invention has a beneficial effect when used to accelerate the stabilization treatment of the rust layer on the surface of weathering steel:

[0071] Test 1: A method for accelerating the stabilization of the rust layer on the surface of weathering steel in this test is carried out according to the steps of Example 1.

[0072] contrast Figure 1 and Figure 2 It can be seen that after the weathering steel is treated in steps (2) and (3) of this test, a porous deposition layer can be formed on the surface, which is conducive to the formation of corrosion galvanic cells between the gel and the weathering steel matrix and the deposition layer. Figure 3 It can be seen that after pulse electroplating and double pulse electroplating, the weathering steel was coated with gel. After 15 days, the original deposition layer structure on the surface had disappeared, but a rust layer with a relatively dense structure was formed.

[0073] Test 2: This test is a method for accelerating the stabilization of the rust layer on the surface of weathering steel, and is carried out according to the steps of Example 2.

[0074] Test 3: This test is a method for accelerating the stabilization of the rust layer on the surface of weathering steel, and is carried out according to the steps of Example 3.

[0075] Test 4: This test is a method for accelerating the stabilization of the rust layer on the surface of weathering steel, and is carried out according to the steps of Example 4.

[0076] Test 5: This test is a method for accelerating the stabilization of the rust layer on the surface of weathering steel, and is carried out according to the steps of Example 5.

[0077] In experiments 1 to 5, no floating rust appeared on the surface of the weathering steel after accelerated surface rust stabilization treatment. The treated weathering steel was immersed in 3.5 wt% NaCl solution for electrochemical testing and compared with the untreated weathering steel. The open circuit potential results are shown in Table 1. The electrochemical impedance spectrum measured at the open circuit potential is shown in Table 1. Figure 4 As shown, after fitting the electrochemical impedance spectrum using the equivalent circuit of R(QR), the fitting results of the corrosion resistance are shown in Table 2.

[0078] Table 1 Open circuit potential of weathering steel after different treatments in 3.5 wt% NaCl solution

[0079] Test 1 Test 2 Test 3 Test 4 Test 5 Unprocessed Open circuit potential (V vs SCE) -0.289 V -0.207 V -0.186 V -0.275 V -0.194 V -0.588 V

[0080] Table 2 Corrosion resistance of weathering steel after different treatments in 3.5 wt% NaCl solution

[0081] Test 1 Test 2 Test 3 Test 4 Test 5 Unprocessed Corrosion resistance (Ω) 21875 23568 24002 22807 24661 2909

[0082] It can be seen from Table 1 that after the treatments from Test 1 to Test 5, the open circuit potential of the weathering steel in 3.5 wt% NaCl solution shifted significantly positively compared with the untreated weathering steel, indicating that a protective layer was formed on the surface of the weathering steel that could prevent the corrosive medium from corroding the substrate. Figure 4 It can be seen that after the treatments of tests one to five, the electrochemical impedance spectrum of the weathering steel in 3.5 wt% NaCl solution has a larger capacitive arc, that is, a larger corrosion resistance, than that of the untreated weathering steel, which means that the weathering steel after accelerated surface rust layer stabilization treatment has better corrosion resistance.

[0083] Therefore, after the treatment of tests one to five, weathering steel can form a rust layer with excellent protective performance in a short time. Compared with untreated weathering steel, the formation time of the stabilized rust layer is shortened, and the corrosion resistance is significantly improved, which can play a good role in promoting the extension of the life cycle of weathering steel.

[0084] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for accelerating the stabilization of the rust layer on the surface of weathering steel, characterized in that: The method comprises the following steps: (1) Preparation of pulse plating solution: Weigh citric acid and dissolve it in water, then dissolve hydroquinone, thiourea and 5,5-dimethylhydantoin, then add copper powder and cobalt hydroxide, stir at 60-80 °C and filter out insoluble matter, then adjust the pH by adding sodium citrate, and finally add sodium sulfide solution to prepare the pulse plating solution; (2) Pulse plating: The weathering steel with the oil removed from the surface is connected to the negative electrode of the pulse power supply, and the copper plate is connected to the positive electrode of the pulse power supply. The two electrodes are separated by a sponge soaked in the pulse plating solution. The pulse power supply is set to output a steady current. After electroplating, the pulse plating is completed. The parameters of a single pulse cycle in the pulse plating process are set as follows: the output peak current is 18~22.5A, the duty cycle is 10~20%, and the frequency is 100~200 Hz; (3) Double pulse electroplating: the weathering steel treated in step (2) is connected to the negative electrode of the double pulse power supply, and the copper plate is connected to the positive electrode of the double pulse power supply. The two electrodes are separated by a sponge soaked in a pulse plating solution, and the double pulse power supply is set to output a steady current. After electroplating, the double pulse electroplating is completed; wherein the parameters of a single pulse cycle in the double pulse electroplating process are set as follows: the output positive pulse peak current is 18-22.5 A, the duty cycle is 10-20%, the frequency is 50-100 Hz, and the number of pulses is 1; the output negative pulse peak current is 27-33.75 A, the duty cycle is 10-20%, the frequency is 100-200 Hz, and the number of pulses is 1; (4) applying gel: applying gel on the surface of the weathering steel after the treatment in step (3), keeping the gel moist and aging the rust layer in an open space outdoors for more than 15 days to complete the process of accelerating the stabilization of the rust layer of the weathering steel; wherein the composition of the gel is, by mass percentage: 1-2 wt% agar, 2-3 wt% sodium polyphosphate, 0.05-0.1 wt% tannic acid, 3-5 wt% sodium chloride, and the rest is water.

2. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1), the feeding ratio of citric acid, water, hydroquinone, thiourea, 5,5-dimethylhydantoin, copper powder, cobalt hydroxide and sodium sulfide solution is (40-50) g: (850-950) mL: (6-8) g: (80-100) g: (15-20) g: (15-20) g: (3-5) g: (40-60) mL, and the concentration of the sodium sulfide solution is 2-3 g / L.

3. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1), the particle size of the copper powder is 500-300 mesh.

4. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1), in step (1), stirring is performed for 4.5 to 5.5 hours; preferably, stirring is performed for 5 hours.

5. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1), the pH is adjusted to 4.5-5.5; preferably, the pH is adjusted to 5.

6. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (2), the electroplating time is 0.5-1.5 min; preferably, the electroplating time is 1 min.

7. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1) and step (3), the electroplating time is 3 to 5 minutes.

8. The method for accelerating the stabilization of the rust layer on the surface of weathering steel as claimed in claim 1, characterized in that: In step (1), the pulse plating solution used in step (2) and step (3) has an operating temperature of not less than 45°C.

9. The rust layer on the surface of weathering steel prepared by the method according to any one of claims 1 to 8.

10. Weathering steel having the surface rust layer according to claim 9.

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