Preparation method of corrosion-resistant conductive grounding carbon steel in-situ coating

Abstract

The present invention relates to a method for preparing a corrosion-resistant grounded carbon steel in-situ coating, comprising the following steps: (1) pretreatment of the carbon steel surface; (2) placing the treated carbon steel as an anode and a graphite plate as a cathode in an in-situ electrolyte and subjecting the electrolytic treatment to a certain period of time; (3) placing the carbon steel treated in step (2) in an in-situ post-treatment solution and stopping the post-treatment after a certain period of time. The method of the present invention overcomes the shortcomings of poor adhesion of externally applied coatings and easy shedding. At the same time, it avoids the problems of long-term consumption and maintenance of electrochemical protection technology. On the basis of ensuring the conductivity and drainage of carbon steel materials, the corrosion morphology is controlled to be uniform corrosion, which greatly reduces the corrosion rate of carbon steel materials in soil, and ultimately enables the grounded carbon steel to meet the service life requirements of the design.

Description

Technical Field

[0001] The invention belongs to the field of material corrosion and protection, and relates to the corrosion resistance technology of conductive grounded carbon steel, in particular to a preparation method of a corrosion-resistant conductive grounded carbon steel in-situ coating. Background Art

[0002] Carbon steel is a common buried drainage material for grounding grids, but corrosion is inevitable during service. Therefore, anti-corrosion technical protection is required. The main protection technologies currently include hot-dip galvanizing, hot-dip copper, conductive coatings and other coating treatment technologies, and cathodic protection technology; the technical principles of the above methods can be divided into two categories: one is that the protector (zinc, sacrificial anode, current source) provides electrons to the protected body (carbon steel) to avoid corrosion of the grounding material; the other is to protect the substrate through the isolation effect of a higher potential protective layer (copper) or an organic coating. However, the above technologies have the following defects: cathodic protection technology has the disadvantage of continuous consumption of resources; external coatings have poor adhesion and uneven coatings, resulting in small anodes and large cathodes, which leads to the risk of local shedding. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a grounded carbon steel in-situ coating that can control the corrosion morphology of carbon steel to uniform corrosion and reduce the corrosion rate of carbon steel materials in soil.

[0004] The technical solution adopted by the present invention to solve the technical problem is:

[0005] A method for preparing a corrosion-resistant grounding carbon steel in-situ coating comprises the following steps:

[0006] (1) Carbon steel surface pretreatment;

[0007] (2) using the treated carbon steel as an anode and the graphite plate as a cathode, placing them in an in-situ electrolyte and subjecting them to electrolytic treatment for a certain period of time, wherein the components and contents of the in-situ treatment solution are as follows: 5-10 g / L sodium aluminate, 5-10 g / L sodium hexametaphosphate, 3-6 g / L sodium carbonate, 10-30 mL / L polyaniline, 10-15 mL / L polypyrrole, 10-30 mL / L polyphenylene vinylene, 10-20 g / L sodium orthovanadate, 2-4 g / L ferrous sulfate, and 10-15 g / L potassium fluoride;

[0008] Among them: sodium aluminate and sodium hexametaphosphate are used to promote the formation of a corrosion-resistant oxide film on the surface of carbon steel under strong electricity; sodium carbonate is used to adjust the pH value of the in-situ treatment liquid; polyaniline, polypyrrole, and polyphenylene vinylene are doped in the coating to form a conductive band; the remaining components can reduce the porosity of the oxide film.

[0009] The combination of the above components and the above content range of each component are determined through a large number of experiments. The above combination and content enable the coating of the present invention to have an excellent balance of corrosion potential, surface morphology and corrosion rate.

[0010] (3) Placing the carbon steel treated in step (2) in an in-situ post-treatment liquid, and stopping the post-treatment for a certain period of time.

[0011] Moreover, the carbon steel surface pretreatment in step (1) includes degreasing and grinding.

[0012] Moreover, the temperature of the electrolytic treatment in step (2) is controlled at 35-45° C., the stirring speed is controlled at 200-400 r / min, the current is controlled at 0.5-1 A, the frequency is controlled at 50-150 Hz, and the treatment time is controlled at 30-45 min.

[0013] Moreover, in step (2), the carbon steel surface area: the graphite plate surface area = 1:10 to 1:20.

[0014] Moreover, the components and contents of the in-situ post-treatment liquid in step (3) are: 10-20 mL / L polyurea, 10-20 mL / L polyaniline, 5-10 g / L sodium dihydrogen phosphate, and 2-4 g / L sodium hydroxide.

[0015] Moreover, the in-situ post-treatment temperature in step (3) is controlled at 45-55° C., and the time is controlled at 60-120 min.

[0016] The advantages and positive effects of the present invention are:

[0017] The method of the present invention overcomes the disadvantages of poor adhesion and easy shedding of external coatings. At the same time, it avoids the problem of long-term consumption and maintenance of electrochemical protection technology. On the basis of ensuring the conductivity and drainage of carbon steel materials, the corrosion morphology is controlled to be uniform corrosion, which greatly reduces the corrosion rate of carbon steel materials in soil, and finally makes the grounded carbon steel meet the service life required by the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The macroscopic morphology of Q235 carbon steel material before and after treatment, where (a) is before treatment and (b) is after treatment;

[0019] Figure 2 The microscopic surface morphology of Q235 carbon steel material after treatment;

[0020] Figure 3 This is the cross-sectional morphology of the Q235 carbon steel material after treatment;

[0021] Figure 4 Polarization curves (logarithmic relationship between potential and current density) of carbon steel material before and after treatment

[0022] Figure 5 The corrosion rate of carbon steel material in chloride ion solution before and after treatment (average corrosion rate after immersion for 30 days), where (a) is before treatment and (b) is after treatment. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0024] Example 1

[0025] A method for preparing a corrosion-resistant grounding carbon steel in-situ coating comprises the following steps:

[0026] (1) Carbon steel surface pretreatment: wipe the carbon steel with ethanol solution and then sand it with 100# silicon carbide sandpaper for 10 minutes;

[0027] (2) The treated carbon steel is used as the anode and the graphite plate is used as the cathode. The surface area ratio of the carbon steel to the graphite plate is 1:20. Place it in the in-situ electrolyte. The electrolyte temperature is controlled at 40°C. The stirring speed is 300r / min. The DC power supply is set to 0.5A current and 50Hz frequency. The power is turned on for in-situ treatment. Stop after 30 minutes of treatment.

[0028] Electrolytic treatment for a certain period of time, the components and contents of the in-situ treatment solution are: 5g / L sodium aluminate, 5g / L sodium hexametaphosphate, 3g / L sodium carbonate, 10mL / L polyaniline, 10mL / L polypyrrole, 10mL / L polyphenylene vinylene, 10g / L sodium orthovanadate, 2g / L ferrous sulfate, 10g / L potassium fluoride, a total of 5L of the original treatment solution;

[0029] (3) The carbon steel treated in step (2) is placed in an in-situ post-treatment solution, wherein the post-treatment solution comprises 10 mL / L polyurea, 10 mL / L polyaniline, 5 g / L sodium dihydrogen phosphate, and 2 g / L sodium hydroxide. The heating is stopped after 60 min in a 50°C water bath.

[0030] A conductive coating was obtained, and then the corrosion potential and corrosion rate of the coating were tested. The test results are listed in Table 1.

[0031] Example 2

[0032] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0033] Example 3

[0034] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0035] Example 4

[0036] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0037] Comparative Example 1

[0038] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0039] Comparative Example 2

[0040] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0041] Comparative Example 3

[0042] The method of Example 1 was repeated with the contents of the components specified in Table 1 below, and the test results are listed in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] The test data of corrosion potential and corrosion rate of each embodiment and comparative example in Table 1 above illustrate that the in-situ electrolyte composition of the present invention is significantly superior to the electrolyte composition of the comparative example in terms of both single performance and comprehensive performance.

[0047] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing a corrosion-resistant grounding carbon steel in-situ coating, characterized in that: The steps include: (1) Carbon steel surface pretreatment; (2) The treated carbon steel is used as an anode and the graphite plate is used as a cathode, and the two are placed in an in-situ electrolyte for electrolysis for a certain period of time. The components and contents of the in-situ electrolyte are as follows: 5-10 g / L sodium aluminate, 5-10 g / L sodium hexametaphosphate, 3-6 g / L sodium carbonate, 10-30 mL / L polyaniline, 10-15 mL / L polypyrrole, 10-30 mL / L polyphenylene vinylene, 10-20 g / L sodium orthovanadate, 2-4 g / L ferrous sulfate, and 10-15 g / L potassium fluoride; (3) Placing the carbon steel treated in step (2) in an in-situ post-treatment solution, and stopping the post-treatment for a certain period of time. The components and contents of the in-situ post-treatment solution are: 10-20 mL / L polyurea, 10-20 mL / L polyaniline, 5-10 g / L sodium dihydrogen phosphate, and 2-4 g / L sodium hydroxide.

2. The method for preparing the corrosion-resistant grounding carbon steel in-situ coating according to claim 1 is characterized in that: Step (1) Carbon steel surface pretreatment includes degreasing and grinding.

3. The method for preparing the corrosion-resistant grounding carbon steel in-situ coating according to claim 1 is characterized in that: In step (2), the temperature of the electrolytic treatment is controlled at 35-45° C., the stirring speed is controlled at 200-400 r / min, the current is controlled at 0.5-1 A, the frequency is controlled at 50-150 Hz, and the treatment time is controlled at 30-45 min.

4. The method for preparing the corrosion-resistant grounding carbon steel in-situ coating according to claim 1 is characterized in that: Step (2) Carbon steel surface area: graphite plate surface area = 1:10~1:

20.

5. The method for preparing the corrosion-resistant grounding carbon steel in-situ coating according to claim 1 is characterized in that: In step (3), the in-situ post-treatment temperature is controlled at 45-55°C and the time is controlled at 60-120 min.

Images